Peptide Dosage Calculator
TL;DR
To reconstitute a peptide, divide the vial's mg by the mL of bacteriostatic water you add to get the mg/mL concentration. To find dose volume, divide your desired dose (in mg) by that concentration. Multiply mL by 100 for insulin-syringe units.
Example: 10 mg peptide + 2 mL BAC water = 5 mg/mL. A 250 mcg dose = 0.05 mL = 5 units on an insulin syringe.
Peptide Dosage Calculator
Calculate reconstitution and per-dose volumes in seconds.
Reconstitution
Dosage
Results
What is peptide reconstitution?
Peptide reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide powder into a sterile liquid solvent — almost always bacteriostatic water (0.9% benzyl alcohol) — so it can be measured and drawn into a syringe. Lyophilized peptides ship as a dry powder because they're chemically stable in that form for years; once mixed with water, the clock starts on a 28–90 day window depending on the peptide.
What supplies do I need to reconstitute a peptide?
- Lyophilized peptide vial — sealed, refrigerated until use
- Bacteriostatic water — 30 mL multi-dose vial is standard
- Mixing syringe — 3 mL syringe with a 21–23 G drawing needle
- Insulin syringes — 0.3 mL, 0.5 mL, or 1 mL units (29–31 G)
- Alcohol prep pads — 70% isopropyl
- Sharps container — for needle disposal
How do I reconstitute a peptide step by step?
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Sanitize both vial stoppers
Wipe the rubber septum of both the peptide vial and the BAC water vial with a fresh alcohol prep pad. Let air-dry for 10 seconds.
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Draw your bacteriostatic water
Use a 3 mL syringe to draw the calculated volume (use the calculator above). Most protocols use 1–3 mL per vial. More water = lower concentration = larger draw volume per dose.
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Inject slowly down the vial wall
Angle the needle so the water trickles down the inside of the glass — not directly onto the powder. Direct stream can damage delicate peptide bonds and cause foaming.
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Swirl gently — do not shake
Roll the vial between your palms for 20–30 seconds until the powder fully dissolves. Shaking creates foam and can denature peptides like BPC-157, Semaglutide, and TB-500.
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Inspect the solution
It should be completely clear and colorless. Cloudiness, particles, or a yellow tint mean the peptide is degraded or contaminated — discard it.
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Label and refrigerate immediately
Write the reconstitution date and concentration directly on the vial. Store at 36–46°F (2–8°C). Use within 28 days for most peptides.
How much bacteriostatic water should I add to a peptide vial?
The answer depends on your dose size and how precisely you want to draw it. Less water makes a stronger concentration (smaller draw volume, harder to measure tiny doses). More water makes a weaker concentration (larger draw volume, easier to measure but uses BAC water faster).
| Vial size | BAC water added | Concentration | 1 unit (insulin syringe) = |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 50 mcg |
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg |
| 5 mg | 2.5 mL | 2 mg/mL | 20 mcg |
| 10 mg | 1 mL | 10 mg/mL | 100 mcg |
| 10 mg | 2 mL | 5 mg/mL | 50 mcg |
| 10 mg | 3 mL | 3.33 mg/mL | 33.3 mcg |
| 15 mg | 3 mL | 5 mg/mL | 50 mcg |
| 20 mg | 2 mL | 10 mg/mL | 100 mcg |
How do I calculate the peptide dose?
The math is two steps:
- Concentration = peptide mg ÷ BAC water mL
- Dose volume (mL) = desired dose mg ÷ concentration mg/mL
Convert mcg to mg by dividing by 1,000 (250 mcg = 0.25 mg). Convert mL to insulin units by multiplying by 100 (0.05 mL = 5 units).
Worked example: 250 mcg BPC-157 dose
Vial is 10 mg BPC-157. You add 2 mL bacteriostatic water.
- Concentration = 10 ÷ 2 = 5 mg/mL
- Dose in mg = 250 ÷ 1,000 = 0.25 mg
- Dose volume = 0.25 ÷ 5 = 0.05 mL
- Insulin units = 0.05 × 100 = 5 units
How do I read an insulin syringe?
Insulin syringes are marked in units (originally for insulin IU), not mL. The conversion is fixed:
| Syringe size | Total capacity | Each tick mark = | Best for |
|---|---|---|---|
| 0.3 mL | 30 units | 0.5 units (0.005 mL) | Micro-doses (10–60 mcg) |
| 0.5 mL | 50 units | 1 unit (0.01 mL) | Most peptide doses (50–500 mcg) |
| 1 mL | 100 units | 2 units (0.02 mL) | Larger doses (Tirzepatide, Retatrutide) |
How long do reconstituted peptides last in the fridge?
Stability depends on the peptide. Refrigerated at 2–8°C (36–46°F) in bacteriostatic water:
| Peptide | Refrigerated stability | Notes |
|---|---|---|
| BPC-157 | 30 days | Light-sensitive; store in original vial |
| TB-500 | 30 days | Stable, low degradation |
| Ipamorelin | 30 days | Avoid temperature swings |
| CJC-1295 (no DAC) | 21 days | Shorter half-life form |
| CJC-1295 w/ DAC | 30 days | More stable |
| Semaglutide | 56 days | Highly stable, GLP-1 analog |
| Tirzepatide | 30–42 days | Manufacturer-dependent |
| Retatrutide | 30 days | Limited published data |
| GHK-Cu | 14 days | Copper complex degrades faster |
| Melanotan II / PT-141 | 30 days | Light-sensitive |
What are the most common peptide reconstitution mistakes?
- Shaking the vial — denatures fragile peptide bonds. Swirl only.
- Injecting water directly onto the powder — causes foaming. Trickle down the wall.
- Using sterile (non-bacteriostatic) water — no preservative means contamination within days.
- Storing at room temperature — accelerates degradation by 5–10× vs refrigerated.
- Mismatching syringe size to dose — a 1 mL syringe makes a 5-unit dose nearly impossible to measure accurately.
- Forgetting to label — within a week you won't remember the concentration or date.
- Reusing needles — dull needles damage tissue and the rubber septum, increasing contamination risk.
Frequently asked questions
Can I use regular distilled water instead of bacteriostatic water?
No. Distilled or sterile water contains no preservative, so once a needle punctures the vial the solution is contaminated within 1–2 days. Bacteriostatic water contains 0.9% benzyl alcohol that prevents microbial growth for ~28 days at refrigerated temperatures.
How accurate do my measurements need to be?
For most peptides a ±5% margin is acceptable. The single biggest accuracy lever is matching syringe size to dose volume — a 0.3 mL syringe with half-unit markings will measure a 5-unit dose far more accurately than a 1 mL syringe with 2-unit markings. Use the calculator above to find the volume, then pick the smallest syringe that fits that draw.
What does it mean if my reconstituted peptide is cloudy?
Cloudiness typically means one of three things: the peptide didn't fully dissolve (swirl longer at room temperature), the solution is contaminated (discard), or the peptide has degraded past usable potency (discard). A properly reconstituted peptide should be water-clear and colorless. A faint yellow tint can be normal for some peptides like Melanotan II.
Can I mix two peptides in the same syringe?
Many common combinations are stable when drawn into the same insulin syringe immediately before injection — Ipamorelin + CJC-1295 is the textbook example. However, mixing peptides in the same vial for long-term storage is not recommended because chemical interactions can degrade one or both peptides over days. Draw, mix in the syringe, inject within minutes.
Why does my vial have less liquid than I added?
Lyophilized peptide powder is sometimes packaged under vacuum. When you add bacteriostatic water, a few drops can be drawn back into the mixing syringe as the pressure equalizes. This is normal — the actual peptide concentration is still correct as long as you injected the full calculated volume of BAC water.
What if my dose doesn't appear in the calculator's preset list?
Select "— Custom —" from the preset dropdown and manually enter your vial size in milligrams. The calculator works for any peptide regardless of whether it's in the preset list — the math is identical (mg per mL → dose mg → volume mL → units).
How do I know which syringe size to buy?
For typical peptide doses (50–500 mcg) the 0.5 mL / 50-unit insulin syringe is the most versatile. Choose 0.3 mL / 30-unit if you're regularly drawing under 10 units (better precision at small volumes). Use 1 mL / 100-unit only if you're dosing larger compounds like Tirzepatide or Retatrutide at multi-mg doses.