Reconstitution reference
Peptide Reconstitution — Free Calculator & Reference
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What is peptide reconstitution and how is the math computed?
Peptide reconstitution is dissolving a lyophilized vial in bacteriostatic water to produce a known concentration in mg/ml. The arithmetic is vial mass ÷ BAC water volume = mg/ml. Target dose ÷ concentration = draw volume; multiply by 100 for U-100 units. A 5 mg vial in 2 ml BAC water yields 2.5 mg/ml — a 250 mcg dose draws 10 units.
The three formulas
- Concentration = vial mass (mg) ÷ BAC water (ml) = result in mg/ml.
- Draw volume = target dose ÷ concentration = result in ml.
- U-100 units = draw volume (ml) × 100.
Reference table
| Vial | BAC water | Concentration | Example dose | U-100 units |
|---|---|---|---|---|
| 2 mg | 1 ml | 2 mg/ml | 200 mcg | 10 units |
| 5 mg | 2 ml | 2.5 mg/ml | 250 mcg | 10 units |
| 5 mg | 3 ml | 1.67 mg/ml | 300 mcg | 18 units |
| 10 mg | 2 ml | 5 mg/ml | 500 mcg | 10 units |
| 10 mg | 5 ml | 2 mg/ml | 1 mg | 50 units |
Why pick a specific BAC water volume?
There is no single "correct" BAC volume — it is a readability choice. Most research protocols pick a volume so that a typical dose lands between 10 and 50 units on a U-100 syringe — readable without micropipetting. The volume choice does not change the total mass available in the vial.
Common reconstitution mistakes
- Mixing up mcg and mg. 1 mg = 1,000 mcg. A "250 dose" is ambiguous without units.
- Mixing up U-100 and U-40. 10 units on U-100 is 0.1 ml; 10 units on U-40 is 0.25 ml.
- Forgetting that BAC water choice changes units, not mass. A higher BAC volume means more units drawn for the same mass dose.
- Re-running the math on every dose. Save the reconstitution mix in Peptly and reload it in one tap; the math stays consistent across the cycle.
See also
- Main peptide calculator page
- BAC water calculator
- Step-by-step reconstitution guide
- BPC-157 reconstitution reference
- Semaglutide reconstitution reference
Frequently asked questions
What does "peptide reconstitution" mean? +
Reconstitution is dissolving a lyophilized (freeze-dried) peptide powder in a liquid — almost always bacteriostatic water (BAC water) — to produce an injectable solution. The result is a known concentration in mg/ml that the user can draw doses from.
Why bacteriostatic water specifically? +
Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits microbial growth in a multi-use vial. Sterile water is suitable for single use but does not preserve a multi-day reconstituted vial. Saline can interact with some peptides.
How long does reconstituted peptide last? +
Most peer-reviewed research protocols refrigerate reconstituted peptides at 2–8 °C and use within 2–4 weeks. Lyophilized powder typically stores at −20 °C until reconstitution. Stability varies by compound — consult primary sources.
Why does my unit count change when I change BAC water volume? +
More water dilutes the same vial mass to a lower mg/ml concentration. Lower concentration means more volume (more units on a U-100 syringe) is needed for the same mass dose. The vial mass and the target dose are unchanged.
What syringe should I use? +
U-100 insulin syringes are the most common reference scale (100 units = 1 ml). Peptly defaults to U-100 and supports U-40 as a setting. The visual syringe view shows the exact draw mark in either scale.