Reconstitution: What You Are Actually Doing

Peptides are supplied as a lyophilised (freeze-dried) powder, typically in glass vials sealed with a rubber stopper. The powder has no volume — it is a solid. Before injection, you must dissolve it in bacteriostatic water (BAC water) to create a liquid solution at a known concentration.

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol. The benzyl alcohol prevents microbial growth, allowing the reconstituted solution to remain stable for 4–6 weeks when stored correctly at 2–8°C. Standard sterile water without benzyl alcohol provides no microbial protection and should not be used for multi-dose vials.

Why Water Volume Determines Everything

The volume of BAC water you add sets the concentration of the final solution. If you add 1 ml to a 5 mg vial, you get 5000 mcg/ml. If you add 2 ml, you get 2500 mcg/ml. This concentration then determines how many units you draw for any given dose. Using the wrong volume — or forgetting what volume you used — is the root cause of most peptide dosing errors.

The peptide dosage calculator above handles all of this math automatically. You only need to know three things: the vial's mg content (printed on the label), how many ml of BAC water you added, and what dose in mcg your protocol calls for.

Reading a U-100 Insulin Syringe Correctly

A standard U-100 insulin syringe holds 1 ml of liquid, divided into 100 equal units. Each unit equals 0.01 ml. The syringe markings go from 0 to 100 in increments of 1, 2, or 5 units depending on the model. This is the standard syringe for peptide administration — not a standard 1 ml or 3 ml syringe, which has different markings.

Units vs ml vs cc

On a U-100 syringe: 10 units = 0.1 ml = 0.1 cc. These are equivalent. If your peptide dosage calculator output is 20 units, that is the same as drawing to the 20-mark on the syringe barrel. The ml and cc equivalents are shown in the calculator output as a reference, but the unit mark is what you use physically.

Syringe Sizes

U-100 syringes come in 0.3 ml (30 units), 0.5 ml (50 units), and 1 ml (100 units) barrel sizes. For peptide work, a 0.5 ml or 1 ml syringe is most practical. Needle gauge: 29–31 gauge is standard for subcutaneous peptide injections. Length: 8 mm (5/16 inch) is typical for subcutaneous administration.

6 Things That Affect Peptide Dosage Calculator Accuracy

• 1. Vial content vs labelled content. Research-grade peptides may have slight variance in actual peptide content vs the label. High-purity pharmaceutical-grade peptides (verified by HPLC) are the most reliable. This calculator assumes 100% of labelled content is present.
• 2. Water volume must be exact. Use a precision syringe to measure BAC water — do not estimate. Adding 1.8 ml instead of 2 ml shifts concentration by 10%, which shifts your dose by 10%.
• 3. mcg vs mg confusion. The most common input error. If your protocol says "250 mcg" and you accidentally enter "250 mg" in the vial field or dose field, the output will be wrong by a factor of 1000. Always check units before calculating.
• 4. Peptide degradation after reconstitution. Reconstituted peptide has a limited shelf life even at 2–8°C. Most sources indicate 4–6 weeks maximum. Beyond this point, potency decreases — the calculator math is still correct but the effective dose decreases. Store lyophilised (unreconstituted) vials at -20°C if not in immediate use.
• 5. Freeze-thaw cycles. Reconstituted peptide solution should never be frozen. Freezing and thawing a reconstituted solution degrades the peptide. Only freeze the original lyophilised powder.
• 6. Syringe type must be U-100. This calculator is calibrated for a U-100 insulin syringe where 100 units = 1 ml. Using a U-40 insulin syringe (used in some veterinary contexts, where 40 units = 1 ml) would require dividing the unit output by 2.5. Standard peptide protocols universally use U-100.

5 Common Peptide Dosage Calculator Mistakes

• 1. Not writing down the water volume used. If you reconstitute a vial and forget how much BAC water you added, every future calculation is guesswork. Write it on the vial with a marker — date, water volume, and expiry (6 weeks from reconstitution).
• 2. Confusing total vial content with dose. The vial contains the full 5 mg. Your dose might be 0.25 mg (250 mcg). These are different numbers. The calculator separates them explicitly — vial mg goes in the top field, dose mcg goes in the bottom field.
• 3. Combining incompatible peptides in the same vial. Some users reconstitute multiple peptides in the same syringe for convenience. This makes accurate dosage calculation impossible unless both compounds are precisely accounted for. Keep separate vials unless your protocol explicitly accounts for this.
• 4. Drawing an air bubble and not accounting for it. A 2-unit air bubble at the top of the syringe means you are getting 2 units less of solution than you think. Always expel air from the syringe before measuring your drawn volume.
• 5. Using expired or improperly stored solution. A calculation that gives 10 units is meaningless if the peptide has partially degraded. Colour change (yellowing), cloudiness, or a precipitate in the reconstituted solution indicates degradation. Discard and reconstitute a new vial.

For all calculators in one place, visit the Fitness Calculators hub. Related tools include the Calorie & TDEE Calculator and the upcoming TRT Dosage Calculator in the TRT & Hormones section.

Using This Peptide Dosage Calculator in Practice

Every time you reconstitute a new vial, run the numbers through this peptide dosage calculator before drawing your first injection. Note the water volume on the vial itself. The three-second calculation eliminates the most common and preventable source of dosing error in peptide protocols.

Pair accurate dosing with appropriate health monitoring. GH secretagogue protocols in particular require baseline fasting glucose and IGF-1 data for meaningful interpretation. The full monitoring framework is in the Bloodwork & Health hub, starting with the Blood Tests Before Steroids panel overview. For PED-related side effect context, see the PED Side Effects hub. New to the site? The Start Here page covers the full content map.