Deca-Durabolin (Nandrolone): Pharmacology, Side Effects, and Bloodwork Impact
DECA-DURABOLIN: SLOW SIZE, LONG TAIL, REAL TRADE OFFS
Deca-Durabolin is nandrolone decanoate, a slow release injectable steroid often just called Deca. It has more controlled trials than almost any other steroid. They show steady lean mass gains, little strength gain, and a drug that stays in the body for months.
This guide covers Deca-Durabolin results, Deca-Durabolin side effects, the "deca dick" question and how a Deca cycle looks in practice. Study figures come from PubMed. Practice figures are marked as practice. The wider family is in nandrolone steroids.
Deca-Durabolin in three numbers
Three numbers sum up what the trials found: the muscle it adds, the strength it does not, and how long it lingers.
A 2026 meta analysis of randomized trials (PMID 41936385).
No significant effect in the same meta analysis (PMID 41936385).
Metabolites in urine in 10 of 12 men after 150 mg (PMID 15713722).
Study figures come from PubMed abstracts. What athletes do in practice is not studied; where we describe it, we say so.
What this Deca-Durabolin guide covers
Deca-Durabolin results from randomized trials in lifters and patients.
Deca-Durabolin side effects: hematocrit, lipids, libido, joints and recovery.
The Deca cycle and stacks athletes report, next to studied doses.
Not coveredA protocol. Nothing here is a dose to take. Practice figures describe what people do, with personal and unstudied risk.
Buying or testing products. Products sold for sport are unregulated.
What Deca-Durabolin is
Nandrolone is testosterone without one carbon atom, which is why it is called a 19-nor steroid. The decanoate ester makes it release slowly from the injection site.
After a single injection, blood levels peaked in 30 to 72 hours. The terminal half life was 7 to 12 days (PMID 15713722).
In the body, nandrolone is turned into dihydronandrolone by the same enzyme that makes DHT from testosterone. Unlike DHT, it is a weaker androgen (PMID 36644692).
Doctors used it for anemia in kidney failure and for wasting. Typical medical doses were 100 to 200 mg a week (PMID 10208142, 11918762).
| Property | Deca-Durabolin (nandrolone decanoate) |
|---|---|
| Form | Oil based intramuscular injection |
| Half life | 7 to 12 days (PMID 15713722) |
| Peak after a shot | 30 to 72 hours (PMID 15713722) |
| 5 alpha reduction | To dihydronandrolone, a weaker androgen (PMID 36644692) |
| Doses in trials | 50 to 600 mg a week (PMID 15713722, 12637255) |
Deca-Durabolin results: what the trials show
Deca-Durabolin has more controlled data than most steroids. The pattern is consistent: lean mass goes up, strength gains are small.
Bodybuilders. 16 men took 200 mg a week or placebo for 8 weeks. Bone free lean mass rose from 59.5 to 63.1 kg, mostly in the trunk and legs (PMID 11354529).
Six weeks after stopping, lean mass was still above baseline. Fat on the legs fell 1.9 percent and stayed lower (PMID 11354529).
Dialysis patients. 100 mg a week for 6 months added 4.5 kg of lean mass, against 1.9 kg on placebo. Walking and stair times improved; grip strength did not (PMID 10208142).
With leg exercise added, both nandrolone and training grew the thigh muscle, and the effects added up (PMID 16825332).
Strength needs training. In men on 600 mg a week, leg strength rose 51 to 63 percent with weight training. Without training it rose 4.7 to 16 percent (PMID 12637255).
The pooled answer. Across 11 randomized trials, nandrolone added 1.59 kg of lean tissue over placebo. It did not change fat mass, grip strength or knee strength (PMID 41936385).
Deca-Durabolin side effects: hematocrit and lipids
Nandrolone raises red blood cells. That is why it was used for anemia.
13 men on peritoneal dialysis took 200 mg a week for 6 months. Hemoglobin rose from 8.5 to 11.7 g/dL and hematocrit from 25.8 to 34.7 percent (PMID 11918762).
In anemic men that is a treatment. In a healthy lifter who starts near normal, the same push can mean thick blood. See hematocrit and hemoglobin.
Lipids look milder than on orals, at first. In 16 bodybuilders, 200 mg a week for 8 weeks did not change HDL, apolipoprotein B or total cholesterol. Lp(a) fell (PMID 15155420).
A 2022 review notes trials of 100 to 200 mg a week left HDL unchanged, but warns the samples were small (PMID 36644692).
Longer use changes the picture. Elderly men on 200 mg a week for 6 months had lower HDL and apolipoprotein A1 and higher triglycerides (PMID 10518249).
Hematocrit rises
Hemoglobin 8.5 to 11.7 g/dL in 6 months at 200 mg a week (PMID 11918762).
HDL falls with time
No change at 8 weeks (PMID 15155420), lower after 6 months (PMID 10518249).
Stacks are worse
Lifters on Dianabol, testosterone and nandrolone together had HDL of 29 vs 61 mg/dL off (PMID 6493049).
Testosterone falls
Dialysis patients on anabolic steroids had testosterone of 205 vs 450 ng/dL (PMID 2805460).
Deca dick: what is known
"Deca dick" is gym slang for low libido or weak erections on nandrolone. No trial has tested it directly, but two facts point the same way.
First, nandrolone becomes dihydronandrolone in tissues where testosterone would become the stronger DHT. So the androgen signal there is weaker (PMID 36644692).
Second, nandrolone shuts down the body's own testosterone. Dialysis patients on anabolic steroids had about half the testosterone of those without (PMID 2805460).
In a Dutch clinic for steroid users, the most common drugs were testosterone, nandrolone and trenbolone. After cycles, 34 percent had low libido and 20 percent erectile dysfunction (PMID 29845939).
That clinic data covers whole stacks, not nandrolone alone. Most users add testosterone to Deca for exactly this reason, to avoid deca dick.
Does Deca-Durabolin help joints?
Deca-Durabolin has a reputation for easing joint pain. The evidence is weak.
A 2016 review says animal models suggest better healing after rotator cuff repair, but human studies are needed (PMID 27141449).
Bone results in people are mixed. The 2026 meta analysis found inconsistent bone density effects, with only the hip showing a gain (PMID 41936385).
In the bodybuilder trial, bone mineral mass did not change in 8 weeks (PMID 11354529).
The long tail: why Deca-Durabolin stays for months
The decanoate ester is long, and nandrolone itself lingers. After one 150 mg injection, metabolites were still in the urine of 10 of 12 men at 6 months (PMID 15713722).
In another study of 11 men, one 150 mg dose was still detectable at 4 months in 6 men. At 9 months it was found in 3 (PMID 26853157).
Even at 50 mg, 16 of 17 men were still positive 33 days later (PMID 15713722).
The Deca cycle: studied doses vs what athletes report
This section describes practice, not advice. Doses athletes report are not studied in healthy people. Using them is a personal, unstudied risk, and every body responds differently.
Trials used 50 to 600 mg a week, for 8 weeks to 6 months (PMID 15713722, 11354529, 12637255, 10208142).
Real users run stacks. In the Dutch clinic, cycles had a median of three steroids, most often testosterone, nandrolone and trenbolone, for a median 10 weeks (PMID 29845939).
In 14 lifters measured in 1984, the stack was 100 to 200 mg of nandrolone a week with testosterone and Dianabol (PMID 6493049).
| Item | In studies | Athletes report (practice, unstudied) |
|---|---|---|
| Weekly dose | 50 to 600 mg (PMID 15713722, 12637255) | Commonly 200 to 600 mg |
| Length | 8 weeks to 6 months | Commonly 10 to 16 weeks; clinic median 10 (PMID 29845939) |
| Base | Alone in most trials | Almost always with testosterone (PMID 29845939) |
| Measured real stack | 100 to 200 mg + testosterone + Dianabol (PMID 6493049) | Same pattern today |
| After the cycle | Detectable for months (PMID 15713722) | Later start of recovery than short esters |
Common Deca-Durabolin stacks athletes report
These are the combinations users describe most. Each compound links to its own guide.
| Stack | Why athletes use it | What the evidence says |
|---|---|---|
| Deca + testosterone | Classic bulk; testosterone covers libido | Most common pairing in clinic data (PMID 29845939) |
| Deca + test + Dianabol | Old school mass stack | Measured: HDL 29 vs 61 mg/dL (PMID 6493049) |
| Deca + test + trenbolone | Hard mass phase | Common in clinic data; no trial (PMID 29845939) |
| Deca vs NPP | NPP is the short ester of nandrolone | Same hormone, faster in and out |
| Deca + Anadrol | Mass and strength | No trial; Anadrol adds liver and lipid load |
Deca-Durabolin and women
In medical trials women got lower doses, for example 100 mg a week against 200 mg for men in dialysis (PMID 16825332).
In 16 women users interviewed in Norway, voice deepening and clitoral enlargement were the hardest effects to live with, and could be irreversible (PMID 32736958).
Because Deca-Durabolin stays for months, any effect that starts can keep building after the last injection (PMID 15713722).
Bloodwork that catches Deca-Durabolin side effects
Each measured effect has a marker. This is what moved in the studies above.
| Marker | What moved | Guide |
|---|---|---|
| Hematocrit, hemoglobin | Hct 25.8 to 34.7% in anemic men, 6 months (PMID 11918762) | CBC markers |
| HDL, triglycerides | No change at 8 weeks; HDL down at 6 months (PMID 15155420, 10518249) | Lipid panel |
| Testosterone | 205 vs 450 ng/dL in patients on steroids (PMID 2805460) | Suppression |
| Creatinine | Rose with muscle gain (PMID 10208142) | Kidney markers |
| Estradiol, prolactin | Not measured in the trials above | Estradiol |
Note on creatinine. It rose about 1.9 mg/dL in dialysis patients on nandrolone, which the authors read as more muscle (PMID 10208142). In lifters, a higher creatinine on Deca needs a kidney check to be read correctly.
7 proven facts about Deca-Durabolin
1. It adds lean mass. 1.59 kg over placebo across 11 trials (PMID 41936385).
2. Strength needs training. No grip or knee strength gain pooled (PMID 41936385).
3. Gains held better. Lean mass still up 6 weeks after stopping (PMID 11354529).
4. It raises hematocrit. Used for anemia: 25.8 to 34.7 percent (PMID 11918762).
5. Lipids hold short term, then slip. No change at 8 weeks, HDL down at 6 months (PMID 15155420, 10518249).
6. It lowers natural testosterone. About half in one patient group (PMID 2805460).
7. It lingers. Detectable up to 9 months after one shot (PMID 26853157).
Deca-Durabolin: frequently asked questions
What does Deca-Durabolin do?
It adds lean mass. Across 11 randomized trials, nandrolone decanoate added 1.59 kg of lean tissue over placebo, without changing grip or knee strength (PMID 41936385).
Is deca dick real?
It is plausible. Nandrolone forms a weaker androgen than DHT in tissues and suppresses natural testosterone. In a steroid clinic, 20 percent had erectile dysfunction after cycles (PMID 36644692, 29845939).
Does Deca-Durabolin help joint pain?
Not proven in people. A review found only animal data for rotator cuff healing (PMID 27141449). Bone density effects in trials were mixed (PMID 41936385).
How long does nandrolone stay in your system?
Long. Half life is 7 to 12 days. After one 150 mg shot, metabolites were found at 6 months in 10 of 12 men (PMID 15713722).
Does Deca-Durabolin raise hematocrit?
Yes. It was used to treat anemia: 200 mg a week raised hematocrit from 25.8 to 34.7 percent in 6 months (PMID 11918762).
Are Deca-Durabolin side effects bad for cholesterol?
Less than orals in the short term. 8 weeks at 200 mg a week did not change HDL (PMID 15155420), but 6 months lowered it in older men (PMID 10518249).
What dose of Deca do athletes use?
Trials used 50 to 600 mg a week. Many users report 200 to 600 mg with testosterone for 10 to 16 weeks. That is practice, not studied, and a personal risk.
What is the difference between Deca and NPP?
Both are nandrolone. Deca is the decanoate ester with a 7 to 12 day half life (PMID 15713722); NPP is a shorter ester. See our NPP guide.
Sources and further reading
Every study figure on this page comes from one of the 16 papers below, checked against PubMed on 1 November 2026. Practice figures are marked as practice. Reference links are dofollow to support open science.
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Final Educational Note
This article is educational and is not medical advice. It reports what trials, clinics and user surveys say about nandrolone decanoate. Practice doses are described, not recommended, and carry personal, unstudied risk.
Headaches, red face, chest pain or one sided leg swelling on a cycle need a doctor, as can thick blood. More guides sit on the steroids hub. Read more on the about page and in the full disclaimer.
