TRT Side Effects: 7 Proven Facts From TRAVERSE and the Label
TRT SIDE EFFECTS: 7 PROVEN FACTS FROM TRAVERSE AND THE LABEL
TRT side effects are better measured than the side effects of almost any other hormone men take, because testosterone replacement therapy has a prescribing label, a 5,246-man randomised safety trial, two older randomised programmes and several meta-analyses of placebo-controlled trials behind it. That record says something more precise than either the clinic brochure or the forum thread: in men who meet the diagnosis and are titrated into the normal range, TRT thickens the blood, raises blood pressure a little, shuts down sperm production, produced more fractures than placebo, and did not increase heart attacks or strokes (PMID 37326322, PMID 38231621, PMID 16339333).
The label adds its own list of TRT side effects seen with androgens as a class, from acne and gynecomastia to venous thromboembolism (Depo-Testosterone prescribing information).
This page sorts the side effects of TRT into three layers: what a trial or the label has measured, what men describe on forums that no trial has counted, and what belongs to a steroid cycle rather than to replacement. Each effect gets the number behind it and the page in this series that covers it in depth. Doses appear only as the label or a trial abstract states them. The full series lives on the TRT and hormones hub.
TRT side effects in brief
Three numbers carry most of what the trials know about the side effects of TRT: how much more often the blood thickens, how much the blood pressure moves, and the one harm nobody expected.
In a meta-analysis of 651 men on testosterone and 433 on placebo treated for at least 90 days, testosterone-treated men were nearly four times as likely to cross a hematocrit of 50 percent; the authors called the rise in hematocrit the most frequent adverse event of replacement (PMID 16339333). A second meta-analysis of 51 studies put the average rise at 3.18 percentage points of hematocrit and 0.80 g/dL of hemoglobin (PMID 20525906).
Awake systolic pressure rose 5.2 mm Hg and sleep systolic pressure 4.3; diastolic moved 1.2 to 1.7. The men whose hematocrit rose most, by 6 to 14 points, had the largest increase, 8.3 mm Hg (PMID 34191621). The FDA added a blood pressure warning to every testosterone product in February 2025 (FDA, February 2025).
A fracture occurred in 91 of 2,601 men on testosterone (3.50 percent) and 64 of 2,603 on placebo (2.46 percent), and the excess appeared for every fracture end point, in a trial that had expected the opposite because testosterone increases bone density (PMID 38231621). Heart attacks and strokes, the harm everyone had expected, did not increase: 7.0 against 7.3 percent, hazard ratio 0.96 (PMID 37326322).
Every figure on this page about TRT side effects is taken from a PubMed abstract, the Depo-Testosterone prescribing information, or an FDA notice, all listed at the end. Where men describe an effect online that no trial has counted, the page says so and marks it as a description. Doses are quoted only where the label or a trial abstract states them.
What this guide to TRT side effects covers
Every one of the TRT side effects with a number: blood thickening and clots, blood pressure, heart rhythm and events, prostate and PSA, bone and fractures, fertility and testicular size, sleep apnea, estradiol, water and mood, each with the trial or label that measured it.
TRT side effects by form: what differs between injections, gel, oral capsules and pellets, including the two risks that belong to one form only.
The side effects of TRT withdrawal, what men describe that no trial has counted, and the monitoring schedule that turns the list into a plan.
Not coveredA dose or a fix for your TRT side effects. Doses are quoted as the label and the trial abstracts state them; what to do about a given lab value is a decision for the prescriber who ordered it.
Women and adolescents. TRT side effects in those groups follow a different profile and are a separate clinical topic; this page is about men.
Each of the TRT side effects in depth. The series has a page for the big ones: high hematocrit on TRT, blood pressure on TRT, water retention on TRT, estradiol on TRT, low libido on TRT, TRT and sleep, TRT and fertility. This page is the map; those are the territory.
All TRT side effects in one table: measured, described, or not TRT
The table is the whole list of TRT side effects in one view. Green means a randomised trial or meta-analysis measured the effect against placebo; amber means the label lists it or the evidence is observational or dose dependent; grey means men describe it but no trial has counted it in replacement doses; red means the effect is real but belongs to doses far above replacement. What is TRT explains where that line sits.
| TRT side effects | What the record shows | Read as |
|---|---|---|
| Thicker blood (erythrocytosis) | Hematocrit above 50 percent almost four times as likely, odds ratio 3.69 (PMID 16339333); average rise 3.18 points (PMID 20525906); short-acting injectables highest (PMID 28526632); the most frequent of all TRT side effects | Most frequent, measured |
| Higher blood pressure | 24-hour systolic up 1.7 to 3.8 mm Hg in ambulatory studies, more in men already hypertensive (PMID 34191621, PMID 34114726); class-wide label warning (FDA, February 2025) | Small, measured, now on the label |
| Atrial fibrillation, pulmonary embolism, kidney injury | More frequent on testosterone in TRAVERSE (PMID 37326322); the arrhythmia signal was not confirmed when all other trials were pooled (PMID 38553429) | Measured in one large trial |
| Venous clots | Labelled risk; short-term odds of venous thromboembolism roughly doubled in a claims database, with and without a hypogonadism diagnosis (PMID 31710339) | Observational plus label |
| Heart attack, stroke | No excess in TRAVERSE, hazard ratio 0.96 (PMID 37326322); none across 106 trials (PMID 38553429); boxed warning language removed (FDA, February 2025) | Measured: no excess in replacement doses |
| Fractures | 3.50 against 2.46 percent, hazard ratio 1.43, despite denser bone (PMID 38231621); the TRT side effects surprise of 2024 | Measured, unexpected |
| Prostate | PSA up about 0.10 ng/mL on average and prostate cancer not increased across 26 trials (PMID 26779889); prostate events detected more often in older trials (PMID 16339333); no excess of cancer or urinary retention in TRAVERSE (PMID 38753865) | Measured: more PSA checks, not more cancer |
| Infertility and smaller testicles | Intratesticular testosterone falls 94 percent on exogenous testosterone (PMID 15713727); sperm recovers in a median 3.4 months after stopping (PMID 16650651); oligospermia on the label (Depo-Testosterone prescribing information); the only one of the TRT side effects that is certain | Certain while on therapy |
| Worse sleep apnea | Oxygen desaturation index worse by 10.3 events per hour at 7 weeks in obese men with severe apnea, no difference by 18 weeks (PMID 22512435) | Measured, time limited |
| Gynecomastia, water, estradiol | Gynecomastia is on the label (Depo-Testosterone prescribing information) and was reported in only 17 percent of randomised trials, none grading it (PMID 42636349); estradiol rises with the dose (PMID 11701431) | Labelled, poorly counted |
| Mood changes, irritability | In TRAVERSE, mood and energy improved modestly against placebo (PMID 38205962); hypomania appeared only at 600 mg a week, in 16 percent of normal men (PMID 10665615) | Replacement improves mood; mania is a cycle dose |
| Acne, oily skin, hair loss | Listed with androgens as a class (Depo-Testosterone prescribing information); no placebo-controlled incidence in replacement trials; the most asked-about TRT side effects and the least counted | Described, not counted |
| Lower HDL cholesterol | Small fall, 0.49 mg/dL across 51 studies (PMID 20525906); fell in proportion to dose in healthy men (PMID 11701431) | Measured, small at replacement doses |
| Injection pain, cough after injection, gel transfer | Injection site inflammation on the label (Depo-Testosterone prescribing information); pulmonary oil microembolism 223 cases per 3.1 million undecanoate injections (PMID 35610506); virilisation of children from gel contact (PMID 23729604) | Form specific |
The pattern is worth stating before the detail. The side effects of TRT that trials have measured are hematological and vascular: thicker blood, slightly higher pressure, more rhythm and clot events in the one trial large enough to see them, and the fracture surprise. The TRT side effects men most often ask about, acne, hair, mood and gynecomastia, are either poorly counted or belong to doses the trials never used. The sections below take the layers one at a time.
Thicker blood: the most common TRT side effect
Testosterone tells the bone marrow to make red cells, partly by suppressing hepcidin so that more iron is available and partly by raising erythropoietin and stimulating the marrow directly (PMID 28526632). That is why it corrects anemia in older men, and it is also why the hematocrit, the share of blood volume made of red cells, is the first of the TRT side effects to show on a lab report. In the 19-trial meta-analysis of men over 45, testosterone-treated men were almost four times as likely to cross 50 percent, odds ratio 3.69 with a confidence interval of 1.82 to 7.51, and the authors named the rise in hematocrit the most frequent adverse event of replacement (PMID 16339333).
The average size of the change is modest. Across 51 comparative studies, hemoglobin rose 0.80 g/dL and hematocrit 3.18 percentage points more than in controls (PMID 20525906); in 30 randomised trials reviewed in 2026, the median hematocrit went from 43 percent at baseline to 45 percent on treatment (PMID 42636349). The distribution is the problem rather than the mean: a minority of men rise far more, and the formulation decides who. Short-acting injectables carry the highest incidence of erythrocytosis, because the peak in the days after an injection drives the marrow hardest (PMID 28526632). The label asks for hemoglobin and hematocrit to be checked periodically to detect polycythemia (Depo-Testosterone prescribing information).
Why thicker blood leads the TRT side effects list is viscosity. Thicker blood is harder to pump and more prone to clot, and the label lists venous thromboembolism, deep vein thrombosis and pulmonary embolism, among the reactions seen with testosterone products, asking that leg pain, swelling, warmth or sudden breathlessness be evaluated at once and the drug stopped if a clot is suspected (Depo-Testosterone prescribing information).
The best population data on TRT side effects and clots are observational: in a case-crossover study of 39,622 men with a first venous thromboembolism, a testosterone prescription in the six months before the event roughly doubled the short-term odds, 2.32 in men with a hypogonadism diagnosis and 2.02 in men without one, with a larger point estimate in men under 65 (PMID 31710339). TRAVERSE, the randomised trial, saw pulmonary embolism more often on testosterone than on placebo (PMID 37326322).
What the trials did not find is a link from the hematocrit itself to heart attacks or strokes at replacement doses; the erythrocytosis review notes that evidence tying testosterone-induced erythrocytosis to arterial events remains limited (PMID 28526632). The practical reading is that a rising hematocrit is the entry on the TRT side effects list that is easiest to see coming and easiest to act on, which is why every guideline schedules it. The mechanics of what a clinic does about it, from dose and frequency changes to phlebotomy, are on high hematocrit on TRT; the lab itself is explained on hematocrit and hemoglobin CBC markers.
Blood pressure: the TRT side effect that changed the label in 2025
For years blood pressure was a footnote in the discussion of TRT side effects. It became a headline because the FDA required ambulatory blood pressure monitoring studies from the makers of the newer products, and the studies agreed with each other. In 138 hypogonadal men taking an oral testosterone undecanoate for four months, 24-hour systolic pressure rose 3.8 mm Hg, awake systolic 5.2 and sleep systolic 4.3, with diastolic changes of 1.2 to 1.7 mm Hg; hematocrit rose 3.2 points at the same time, and the men in the top quartile of hematocrit change, a rise of 6 to 14 points, had the largest systolic increase, 8.3 mm Hg, against 1.9 to 3.3 in the other quartiles (PMID 34191621).
A second oral undecanoate put the same TRT side effects question to 155 men and showed a smaller shift: 1.7 mm Hg at 120 days and 1.8 at 180 in 155 men, but 3.4 against 0.7 mm Hg in men already on antihypertensive drugs, with baseline pressure and antihypertensive use the only predictors (PMID 34114726). The direction was the same for the injectable and transdermal products the agency reviewed, and on 28 February 2025 the FDA announced class-wide label changes for all testosterone products: a new warning that testosterone can increase blood pressure, product-specific ambulatory data where they existed, and removal of the older boxed warning language about cardiovascular risk (FDA, February 2025).
The Depo-Testosterone label now states that testosterone can increase blood pressure, which can increase cardiovascular risk over time, that blood pressure should be monitored periodically, especially in men with hypertension, and that testosterone products are not recommended in uncontrolled hypertension (Depo-Testosterone prescribing information). Two to four millimetres of mercury, as TRT side effects go, is small for one man and large for a population, and the hematocrit link in the first study gives the mechanism a face: the men whose blood thickened most were the men whose pressure rose most. The home monitoring routine and what the numbers mean are on blood pressure on TRT.
Heart rhythm, clots and events: what TRAVERSE measured
The question that hung over TRT side effects for a decade was whether the therapy caused heart attacks and strokes. A 2010 trial in 209 frail older men was stopped early for cardiovascular adverse events (PMID 20592293), and two observational studies in 2013 and 2014 reported more events in treated men, which produced the FDA boxed warning of 2015. The randomised answer came from TRAVERSE: 5,246 men aged 45 to 80 with two fasting testosterone levels below 300 ng/dL, hypogonadal symptoms and existing or high cardiovascular risk, randomised to 1.62 percent testosterone gel titrated to 350 to 750 ng/dL or placebo for a mean 21.7 months of treatment and 33 months of follow-up (PMID 37326322).
The primary end point, death from cardiovascular causes, non-fatal heart attack or non-fatal stroke, occurred in 182 men on testosterone (7.0 percent) and 190 on placebo (7.3 percent), hazard ratio 0.96 with a confidence interval of 0.78 to 1.17, meeting the noninferiority margin. What did increase were atrial fibrillation, acute kidney injury and pulmonary embolism (PMID 37326322). A 2024 meta-analysis of 106 placebo-controlled trials with 8,126 men on testosterone and 7,310 on placebo confirmed no difference in major cardiovascular events and in mortality, and found the excess of arrhythmia only in TRAVERSE itself, not when all other trials were pooled (PMID 38553429).
Two surrogate studies sit on either side of that result. In 138 older men with existing severe atherosclerosis, non-calcified coronary plaque volume grew 41 cubic millimetres more on testosterone than on placebo over a year (PMID 28241355); in TEAAM, 308 men over 60 took gel titrated to 500 to 900 ng/dL for three years and showed no difference in carotid thickness or coronary calcium (PMID 26262795). Neither measured events.
The honest reading of the cardiac side effects of TRT in 2026 is that heart attack and stroke did not increase in men like those in TRAVERSE; that atrial fibrillation and pulmonary embolism did, in that one trial; and that the result says nothing about a man without hypogonadism taking twice the label range, who was never enrolled.
Prostate, PSA and bone: two reassurances and one surprise
Among TRT side effects, the prostate fear is older than the heart fear and has aged worse. In a meta-analysis of 20 cohort estimates, a 5 nmol/L higher natural testosterone carried a relative risk of prostate cancer of 0.99; across 26 randomised TRT trials the average PSA change after starting therapy was 0.10 ng/mL, and across 11 trials the relative risk of prostate cancer as an adverse effect was 0.87 with a wide confidence interval of 0.30 to 2.50 (PMID 26779889). The older meta-analysis found prostate events, PSA above 4, biopsies and cancers taken together, detected more often on testosterone, odds ratio 1.78, with no single component significant on its own (PMID 16339333): more checking, more findings.
TRAVERSE enrolled men screened to exclude high prostate cancer risk and followed them with a standardised monitoring plan. High-grade or any prostate cancer, acute urinary retention, surgery for benign enlargement, biopsy and new drugs for urinary symptoms were all uncommon and did not differ from placebo; PSA rose more on testosterone in the first year (PMID 38753865). Prostate carcinoma remains a labelled contraindication, and the label notes that older men may be at increased risk of prostatic hypertrophy and carcinoma on androgens (Depo-Testosterone prescribing information). The guideline therefore asks for baseline prostate assessment and PSA in men over 40 before TRT and on a schedule afterwards (PMID 29562364).
Bone is where the TRT side effects record turned. Testosterone raised spine trabecular volumetric bone density by 7.5 percent against 0.8 percent on placebo over a year, with estimated bone strength up 10.8 against 2.4 percent (PMID 28241231), and the field expected fewer fractures. TRAVERSE found more: a clinical fracture in 91 of 2,601 men on testosterone against 64 of 2,603 on placebo over a median 3.19 years, 3.50 against 2.46 percent, hazard ratio 1.43 with a confidence interval of 1.04 to 1.97, higher on testosterone for every fracture end point (PMID 38231621). The authors offered no proven mechanism; more activity and more falls in men who feel better is one hypothesis, and it remains a hypothesis.
Fertility and testicular size: the TRT side effects that are certain
Every other entry on the TRT side effects list is a probability. This one is physiology. Testosterone from outside is read by the hypothalamus and pituitary as testosterone, luteinising hormone and follicle-stimulating hormone fall, and the testes stop making both testosterone and sperm. In 29 men with normal reproductive function given 200 mg of testosterone enanthate a week for three weeks, LH and FSH fell to 5 and 3 percent of baseline and intratesticular testosterone fell 94 percent, from 1,234 to 72 nmol/L (PMID 15713727). The label lists oligospermia among the reactions seen with androgens, and lists testicular atrophy, subfertility and infertility among reactions reported in men who misuse higher doses (Depo-Testosterone prescribing information).
Smaller testicles, the most visible of the TRT side effects, follow from the same mechanism, because most testicular volume is sperm-producing tissue that shrinks when it is idle; the trials did not measure volume as an outcome in replacement, so the size of the change is a description, not a figure. Recovery after stopping is measured. In an integrated analysis of 1,549 men whose sperm production had been suppressed by hormonal contraception with testosterone, sperm concentration recovered to 20 million per mL in a median 3.4 months, 67 percent of men by 6 months, 90 percent by 12 and 100 percent by 24, with older age and longer treatment slowing the return (PMID 16650651).
The same hCG study that measured the fall also measured the rescue: 500 IU of hCG every other day alongside the testosterone kept intratesticular testosterone 26 percent above baseline, and 250 IU kept it within 7 percent (PMID 15713727), which is the basis for adding hCG when a man on TRT wants to keep fertility. The guideline's position is simpler: men planning fertility in the near term should not start testosterone (PMID 29562364). The alternatives and the timeline are on TRT and fertility; what the axis does afterwards is on post-cycle therapy.
Sleep apnea, mood and aggression: TRT side effects measured in replacement, mistaken for a cycle
Sleep apnea is a guideline reason not to start TRT when it is severe and untreated (PMID 29562364), and the evidence behind that is one careful trial. Sixty-seven obese men with severe obstructive sleep apnea, all on a weight-loss diet, received 1,000 mg of testosterone undecanoate or placebo at 0, 6 and 12 weeks (PMID 22512435). At 7 weeks testosterone had worsened the oxygen desaturation index by 10.3 events per hour and the time spent below 90 percent oxygen saturation by 6.1 percent; by 18 weeks neither differed from placebo, and the effect did not depend on the men's starting testosterone (PMID 22512435).
The older meta-analysis found no significant difference in sleep apnea frequency across 19 trials (PMID 16339333), and the 2026 review found that only three randomised trials ever reported an incidence (PMID 42636349).
Mood is where forum and trial disagree most about TRT side effects. On TRAVERSE, half the men had significant depressive symptoms at entry; testosterone produced modest but significant improvements in mood and energy against placebo, with no change in cognition or sleep quality (PMID 38205962). The Testosterone Trials found slightly better mood and lower depressive symptom scores (PMID 26886521). Irritability and aggression in replacement doses have not been measured as an excess in any trial on this page.
What has been measured is what happens far above replacement: in 56 normal men given testosterone cypionate rising to 600 mg a week for six weeks, manic scores rose on average, but 84 percent showed minimal change, 12 percent became mildly hypomanic and 4 percent markedly so, with nothing at baseline predicting who (PMID 10665615).
That is the clearest example of a cycle effect being filed under TRT side effects. The label makes the same distinction, listing mania, hostility and aggression among reactions reported in individuals who misuse anabolic steroids rather than among the reactions of replacement (Depo-Testosterone prescribing information). Night sweats, insomnia and snoring in the first weeks are described by men and are reviewed on TRT and sleep; the mood story continues on libido on steroids for the high-dose end.
Estradiol, gynecomastia, water and libido: the aromatase side effects of TRT
Some testosterone is converted to estradiol by aromatase, mostly in fat, and estradiol rises with the testosterone dose: in the dose-response study in healthy young men, estradiol tracked testosterone across the range from 25 to 600 mg a week (PMID 11701431). Estradiol does useful work in men, protecting bone and supporting libido, and a man who crushes it with an aromatase inhibitor usually feels worse.
The side effects of TRT attributed to it are gynecomastia, water retention and swings in sexual desire, and the honest position is that all three are labelled and none is well counted. Gynecomastia appears on the label among reactions seen with androgens (Depo-Testosterone prescribing information); in the 2026 review of 30 randomised trials it was reported in 17 percent of them, and none graded it (PMID 42636349).
Water retention, one of the TRT side effects on the label, is listed as retention of sodium, chloride, water, potassium, calcium and phosphate (Depo-Testosterone prescribing information), and shows up in trials as a change in weight in the first weeks rather than as a counted event. Libido is the clearest case of a side effect running in both directions: the label lists increased or decreased libido (Depo-Testosterone prescribing information); TRAVERSE measured an increase in sexual activity of about half an act per day over placebo, sustained for two years, without improvement in erectile function (PMID 37589949). A man whose libido falls on TRT usually has a reason that bloodwork can find, and low libido on TRT lists seven of them.
None of these TRT side effects is grounds for routine estradiol blockade; the guideline does not include estradiol in the monitoring schedule (PMID 29562364), and the right move when breast tenderness or bloating appears is to measure before acting. The detail, including which assay to ask for and what the numbers mean, is on estradiol on TRT and water retention on TRT; the surgical end of gynecomastia is on how to get rid of gyno.
TRT side effects by form: injections, gel, oral capsules, pellets
Most side effects of TRT come from the molecule and follow the blood level, so every form shares them. A few belong to the delivery route, and two of those are serious enough to have their own warnings. The table separates what is shared from what is specific.
| Form | What differs | Read as |
|---|---|---|
| Cypionate or enanthate injections | Peaks in the days after a dose drive erythrocytosis hardest; short-acting injectables carry the highest incidence (PMID 28526632). Inflammation and pain at the injection site are on the label (Depo-Testosterone prescribing information). Splitting the dose flattens the peak; see TRT injection frequency | Most hematocrit |
| Testosterone undecanoate injection | Oil-based depot; pulmonary oil microembolism, a cough or urge to cough within minutes of the injection, in 223 cases per 3,107,652 injections in one post-market review, almost all resolving within an hour; 88 events across 7,978 patients in 29 studies (PMID 35610506) | Rare, form specific |
| Transdermal gel | Steady levels, less erythrocytosis than injections (PMID 28526632). Skin-to-skin transfer: a 21-month-old boy and a 3-year-old girl developed pubic hair and genital growth after sleeping against fathers who applied gel to their arms and chest; both reversed when exposure stopped (PMID 23729604) | Transfer to children |
| Oral testosterone undecanoate | Taken with meals; the ambulatory blood pressure studies behind the 2025 TRT side effects label change were run on these products, 1.7 to 3.8 mm Hg systolic (PMID 34191621, PMID 34114726). Modern formulations avoid the liver injury of the old 17-alpha-alkylated oral androgens | Pressure data best documented |
| Subcutaneous pellets | High early levels that decline over months; no adjustment once implanted; extrusion and infection at the site are described by men, not counted among TRT side effects in replacement trials | Inflexible |
| Any form at misuse doses | The label lists cardiac arrest, heart attack, cardiomyopathy, heart failure, stroke, liver toxicity, mania, paranoia, psychosis, aggression, dyslipidemia, testicular atrophy and infertility among reactions reported in people who misuse anabolic steroids (Depo-Testosterone prescribing information) | Not TRT |
The gel transfer cases deserve one more sentence because they are the only one of the TRT side effects that lands on someone else. Both children recovered fully once contact stopped (PMID 23729604), and the labelled precautions, covering the site and washing before contact, are what prevent it. The pharmacology of the injectable esters is on testosterone cypionate and testosterone propionate.
Side effects of TRT withdrawal: what stopping does
The side effects of TRT do not end when the injections do, and the reason follows from the fertility section: the axis has been idle, and it does not restart the moment the drug leaves the blood. The measured pieces are three. Sperm production returns over months, a median 3.4 months to 20 million per mL and up to two years for the last men (PMID 16650651).
Insulin sensitivity falls quickly: in 12 men with hypogonadotropic hypogonadism whose replacement was withdrawn for two weeks, testosterone went from 529 to 28 ng/dL, fasting insulin rose from 4.9 to 6.2 microunits per mL, insulin resistance by HOMA rose from 1.07 to 1.4 and the insulin sensitivity index fell from 11.0 to 7.5, with body weight unchanged (PMID 17726076).
The third piece comes from men who stopped much higher doses, and it is the warning for anyone who has drifted above replacement. Among 24 former long-term anabolic steroid users, the 19 who were not on treatment had smaller testicles and testosterone 131 ng/dL lower than non-using weightlifters, five of them below 200 ng/dL despite 3 to 26 months off; 29 percent had had a major depressive episode during withdrawal, and two men had not regained normal libido or erections even on replacement (PMID 25598171). The label describes the same picture in its dependence section, listing withdrawal symptoms such as depressed mood, fatigue, insomnia and loss of sexual drive when misused testosterone is stopped (Depo-Testosterone prescribing information).
For a man on true replacement the question is different, because his axis was already failing before he started; stopping returns him to the hypogonadism that was diagnosed, plus a recovery interval. For a man whose axis was suppressed by the therapy itself, secondary hypogonadism from obesity or opioids for example, recovery is possible and slow, and the symptoms in the gap, low mood, fatigue, flat libido and the insulin shift above, are the side effects of TRT withdrawal that men describe. The clinical approach to restarting the axis is on hormonal recovery after steroids and PCT recovery timeline.
What men describe: TRT side effects no trial has counted
Forum threads about TRT side effects are long and consistent, and most of what they contain is not in the trials, either because it was never measured or because it was measured at doses the writers do not use. Nothing in this section is evidence or a protocol; it is a description of what men report, kept apart from the measured record so that the two are not confused.
What men describe. The most frequent complaints in the first months are acne on the back and shoulders, oilier skin, night sweats, a faster resting heart rate and a feeling of being warm, testicles that visibly shrink, and a libido that surges and then settles (forum posts). Men on injections describe a two-day window after each shot when they feel best and a trough before the next one, and describe moving from one injection a week to two or three to smooth it (forum posts).
Men who had thinning hair describe it accelerating; men who did not describe no change (forum posts). A smaller group describes irritability or a short temper, often alongside a self-prescribed dose of 200 mg a week or more without bloodwork (forum posts).
What is measured among these TRT side effects. Acne, seborrhea, male pattern baldness and hirsutism are on the label as reactions seen with androgens, without a frequency (Depo-Testosterone prescribing information), and no placebo-controlled trial on this page counted them in replacement. Testicular shrinkage follows from a 94 percent fall in intratesticular testosterone (PMID 15713727). The peak-and-trough pattern men describe is pharmacology, and the clinics address it by splitting the dose.
The irritability men describe at 200 mg a week and above is in the direction of the 600 mg trial, where 16 percent of normal men became hypomanic (PMID 10665615), and in the opposite direction of TRAVERSE at replacement levels, where mood improved (PMID 38205962). The line between the two is a blood level, not a feeling; TRT vs steroid cycles puts numbers on it.
Monitoring: how a list of TRT side effects becomes a plan
Every one of the measured TRT side effects on this page has a test attached to it, and the trials were safe because they ran the tests. The Endocrine Society schedule evaluates men on therapy for symptom response and adverse effects with testosterone, hematocrit and prostate assessment at fixed intervals (PMID 29562364); the label asks for periodic hemoglobin and hematocrit, periodic blood pressure, and notes that serum cholesterol may rise and that androgens increase sensitivity to oral anticoagulants (Depo-Testosterone prescribing information).
| Test | Side effect it catches | Read as |
|---|---|---|
| Hemoglobin and hematocrit | Erythrocytosis, the most frequent adverse event (PMID 16339333); periodic checks on the label (Depo-Testosterone prescribing information). See high hematocrit on TRT | Scheduled |
| Blood pressure | The 2025 label warning; monitor periodically, especially with hypertension (Depo-Testosterone prescribing information); the rise tracks the hematocrit (PMID 34191621) | Scheduled |
| Total testosterone at trough | Confirms the target; TRAVERSE titrated to 350 to 750 ng/dL (PMID 37326322). Levels above the range are where the cycle side effects begin (PMID 11701431). See TRT bloodwork | Scheduled |
| PSA and prostate exam | Baseline and scheduled in men over 40 (PMID 29562364); PSA rises more in the first year, cancer did not increase with screening (PMID 38753865) | Scheduled |
| Lipid panel | HDL falls slightly (PMID 20525906); cholesterol may increase on the label (Depo-Testosterone prescribing information). See lipid panel HDL LDL triglycerides | Scheduled |
| Estradiol | Not in the guideline schedule (PMID 29562364); measured when breast tenderness, bloating or libido change appear | If symptoms |
| Sleep study | Severe untreated apnea is a reason not to start (PMID 29562364); breathing worsened at 7 weeks in one trial (PMID 22512435) | If snoring or daytime sleepiness |
| Semen analysis | Sperm production is suppressed on every form and recovers over months (PMID 16650651); men who may want children decide before the first dose | Before starting |
Two tools in this series support the TRT side effects schedule: the hematocrit calculator for reading a CBC against the thresholds the trials used, and the free testosterone calculator for the men whose total number misleads. Neither chooses a dose; both make a prescribed one legible.
Five mistakes men make about TRT side effects
Each comes from reading TRT side effects without their dose, their population or their test.
1. Fearing the heart and ignoring the blood count. Heart attack and stroke did not increase in TRAVERSE (PMID 37326322); hematocrit above 50 percent was almost four times as likely across 19 trials (PMID 16339333). The feared TRT side effects are rare and the common one is on the first page of every lab report.
2. Treating blood pressure as a footnote. It is now a labelled warning on every testosterone product (FDA, February 2025), and the men whose hematocrit rises most see the largest increase, 8.3 mm Hg (PMID 34191621). A home cuff costs less than one lab panel.
3. Blocking estradiol on a feeling. Gynecomastia and water retention are labelled (Depo-Testosterone prescribing information) and poorly counted (PMID 42636349); estradiol is not in the guideline monitoring schedule (PMID 29562364). Measure first; the hormone protects bone and libido.
4. Calling cycle effects TRT side effects. Hypomania appeared at 600 mg a week in 16 percent of normal men (PMID 10665615), not at replacement, where mood improved (PMID 38205962). The label lists mania, aggression and cardiomyopathy under misuse, not under replacement (Depo-Testosterone prescribing information).
5. Discovering the fertility side effects of TRT after the first injection. Intratesticular testosterone falls 94 percent within weeks (PMID 15713727) and sperm take a median 3.4 months to return after stopping (PMID 16650651). The guideline says men planning fertility should not start (PMID 29562364); hCG and sperm banking are conversations for before, not after.
Verdict: the side effects of TRT are real, mostly measurable, and mostly manageable
Read from the label, the meta-analyses and TRAVERSE rather than from either a clinic or a forum, the side effects of TRT in men who meet the diagnosis and stay in the normal range are these: thicker blood in a minority that monitoring catches, a few millimetres of blood pressure that a cuff catches, more atrial fibrillation and pulmonary embolism in the one trial powered to see them, more fractures than anyone predicted, certain loss of sperm production while on therapy with recovery over months after, and no excess of heart attacks, strokes or prostate cancer (PMID 16339333, PMID 34191621, PMID 37326322, PMID 38231621, PMID 16650651, PMID 26779889).
Acne, hair, gynecomastia and water are TRT side effects that are labelled and described but not counted. Mania, cardiomyopathy and the rest of the frightening list belong to doses the trials never gave.
For readers here the practical conclusion is that the question of TRT side effects has a measured answer and a described one, and that the two should not be mixed: the measured list is short and comes with a test for each entry, the described list is long and belongs partly to replacement and partly to doses above it. A man at 550 ng/dL with a hematocrit and a blood pressure on file is managing the first list. A man at 1,300 without either is on the second, whatever he calls it. The series continues on TRT bloodwork, what is TRT and TRT vs steroid cycles; the hub is TRT and hormones.
TRT side effects: frequently asked questions
What are the side effects of TRT?
The side effects of TRT measured against placebo are a higher hematocrit, with a hematocrit above 50 percent almost four times as likely (PMID 16339333), a rise in blood pressure of about 2 to 4 mm Hg systolic (PMID 34191621, PMID 34114726), more atrial fibrillation, pulmonary embolism and acute kidney injury in the TRAVERSE trial (PMID 37326322), more fractures (PMID 38231621), and suppression of sperm production in every man (PMID 15713727). Heart attacks, strokes and prostate cancer did not increase (PMID 37326322, PMID 26779889). Acne, oily skin, hair loss, gynecomastia and water retention are listed on the label but have not been counted in replacement trials (Depo-Testosterone prescribing information).
Is TRT safe long term?
The longest randomised data on TRT side effects come from TRAVERSE, 5,246 men followed for a mean 33 months: no increase in major cardiovascular events, hazard ratio 0.96, but more atrial fibrillation and pulmonary embolism (PMID 37326322) and more clinical fractures, 3.50 against 2.46 percent (PMID 38231621). A meta-analysis of 106 trials found no difference in cardiovascular events or mortality (PMID 38553429). Nothing randomised runs beyond about three years, so long-term means monitored: hematocrit, blood pressure, PSA and lipids on a schedule (PMID 29562364).
What are the side effects of TRT injections specifically?
Injections share every one of the TRT side effects of the molecule itself and add two of their own. Short-acting cypionate and enanthate produce peaks that drive erythrocytosis harder than gels, so injections carry the highest incidence of a raised hematocrit (PMID 28526632), and the label lists inflammation and pain at the injection site (Depo-Testosterone prescribing information). Oil-based testosterone undecanoate injections can cause a brief cough or chest tightness from pulmonary oil microembolism, 223 cases per 3.1 million injections, almost all resolving within an hour (PMID 35610506). Splitting the weekly dose into smaller injections flattens the peaks.
Does TRT cause hair loss or acne?
Male pattern baldness, acne, seborrhea and hirsutism are listed on the Depo-Testosterone label among the reactions seen with androgens as a class, without a frequency (Depo-Testosterone prescribing information). No placebo-controlled trial of replacement on this page counted either as an outcome, so their incidence among TRT side effects is not measured. Men describe acne on the back and shoulders in the first months and acceleration of thinning that had already begun (forum posts). Both are driven by androgen action on skin and follicle and tend to follow the blood level.
What happens when you stop TRT?
The side effects of TRT withdrawal are the axis restarting slowly: the hormone leaves the blood within days to weeks and the production it suppressed takes months to return. Sperm production recovered to 20 million per mL in a median 3.4 months, 90 percent of men by a year and all by two years (PMID 16650651). In 12 hypogonadal men taken off replacement for two weeks, testosterone fell from 529 to 28 ng/dL and insulin sensitivity dropped by about a third (PMID 17726076). Men who stopped much higher doses reported low mood, fatigue, low libido and in 29 percent a major depressive episode during withdrawal (PMID 25598171). A man on true replacement returns to the deficiency he was treated for.
Does TRT shrink your testicles?
Yes, to some degree, in every man on every form; it is one of the TRT side effects that follows from physiology. Exogenous testosterone suppresses LH and FSH, and intratesticular testosterone fell 94 percent in healthy men within three weeks of 200 mg of testosterone enanthate a week (PMID 15713727). Most testicular volume is sperm-producing tissue, which shrinks when idle. Trials of replacement did not measure testicular volume as an outcome, so the size of the change is described rather than counted. Low-dose hCG given alongside testosterone kept intratesticular testosterone in the normal range in the same study (PMID 15713727).
Does TRT raise blood pressure?
Slightly, and it is one of the TRT side effects the FDA now requires every testosterone product to state. In ambulatory monitoring studies, 24-hour systolic pressure rose 3.8 mm Hg in 138 men after four months on one oral testosterone undecanoate (PMID 34191621) and 1.7 to 1.8 mm Hg in 155 men on another, more in men already taking antihypertensive drugs (PMID 34114726). The men whose hematocrit rose most saw the biggest increase, 8.3 mm Hg (PMID 34191621). The label asks for periodic blood pressure monitoring and does not recommend testosterone in uncontrolled hypertension (Depo-Testosterone prescribing information; FDA, February 2025).
Can TRT cause blood clots?
Venous thromboembolism, deep vein thrombosis and pulmonary embolism, is a labelled reaction, and the label asks that leg swelling, pain or sudden breathlessness be evaluated at once (Depo-Testosterone prescribing information). In a case-crossover study of 39,622 men with a first clot, a testosterone prescription in the preceding six months roughly doubled the short-term odds, 2.32 in men with hypogonadism and 2.02 in men without (PMID 31710339). TRAVERSE saw pulmonary embolism more often on testosterone than placebo (PMID 37326322). A high hematocrit, the most common of TRT side effects, raises blood viscosity and is the mechanism most often proposed (PMID 28526632).
Sources and further reading
Every figure on this page about TRT side effects comes from one of the 31 sources below: 29 papers checked against their PubMed abstracts on 2 October 2026, the current Depo-Testosterone prescribing information on DailyMed, and the FDA notice of February 2025. Forum descriptions of side effects are reported as descriptions and carry no reference number. Reference links are dofollow to support open science.
Keep reading
Four pages from the TRT side effects series: the blood count, the pressure, the fertility question, and the definition the side effects hang on.
Final Educational Note
This article is educational and is not medical advice. It reports what randomised trials, meta-analyses, the Depo-Testosterone prescribing information and the FDA say about the side effects of TRT, testosterone replacement therapy, a prescription treatment requiring diagnosis, dosing and monitoring by a licensed clinician, and it reports how some men describe TRT side effects online as a description of experience, not as evidence. Doses appear only as the label or a trial states them; the page gives no schedule or protocol, does not recommend testosterone for any use outside its approved indication, and is not an encouragement to use performance-enhancing drugs, which carry serious health and legal risks. More guides sit on the PED side effects hub.
Chest pain, sudden breathlessness, one-sided leg swelling, a sudden severe headache or weakness, palpitations, a cough or chest tightness in the minutes after an injection, or a sharp drop in urine output on testosterone are clinical findings that a physician should assess at once. Reference ranges and thresholds vary by laboratory and assay. Read more about how this site works on the about page and in the full disclaimer.
