Peptide Dosage Calculator: Reconstitution & Injection Guide
Free peptide dosage calculator. Enter your vial size, bacteriostatic water volume, and desired dose to get exact injection amounts in seconds.
Getting your peptide dose right matters. Too little and you won’t see results. Too much and you risk side effects. This calculator does the math for you — enter your peptide, vial size, and desired dose, and get exact reconstitution and injection amounts.
If you’re new to peptide injections, read our beginner’s guide first. For step-by-step reconstitution instructions, see how to reconstitute peptides.
How the Calculator Works
The math behind peptide dosing is straightforward but easy to mess up:
Concentration = Peptide amount (mcg) ÷ Bacteriostatic water added (mL)
Injection volume = Desired dose (mcg) ÷ Concentration (mcg/mL)
For example, if you add 2 mL of bacteriostatic water to a 5 mg BPC-157 vial:
- Concentration = 5,000 mcg ÷ 2 mL = 2,500 mcg/mL
- For a 500 mcg dose: 500 ÷ 2,500 = 0.20 mL = 20 units on an insulin syringe
Common Reconstitution Ratios
These are the most common reconstitution volumes used by prescribing physicians:
| Peptide | Vial Size | BAC Water | Concentration | Typical Dose | Units to Draw |
|---|---|---|---|---|---|
| BPC-157 | 5 mg | 2 mL | 2,500 mcg/mL | 500 mcg | 20 units |
| Sermorelin | 6 mg | 3 mL | 2,000 mcg/mL | 300 mcg | 15 units |
| CJC-1295/Ipamorelin | 2 mg each | 2 mL | 1,000 mcg/mL | 100/200 mcg | 10/20 units |
| Semaglutide | 5 mg | 2 mL | 2,500 mcg/mL | 500 mcg | 20 units |
| GHK-Cu | 5 mg | 2 mL | 2,500 mcg/mL | 200 mcg | 8 units |
| AOD-9604 | 5 mg | 2 mL | 2,500 mcg/mL | 300 mcg | 12 units |
Important Dosing Tips
Start Low
If this is your first time with a peptide, start at the low end of the dose range. You can always increase — you can’t undo a dose that’s too high. Your prescribing physician should provide a titration schedule.
Syringe Selection Matters
Use a 100-unit insulin syringe (1 mL) for most peptides. The fine gauge (29-31G) minimizes pain and the 100-unit markings make accurate dosing easy. For very small doses (under 5 units), consider a 0.3 mL/30-unit syringe for better precision.
Storage After Reconstitution
Once you add bacteriostatic water, store the vial in the refrigerator (36-46°F / 2-8°C). Most reconstituted peptides remain stable for 28-30 days when properly refrigerated. Never freeze a reconstituted vial.
Injection Sites
Rotate your injection sites to prevent lipodystrophy. The abdomen (2+ inches from the navel) is the most common subcutaneous site, followed by the outer thigh and back of the arm.
Understanding Insulin Syringe Units
This trips up a lot of people. On a standard 100-unit insulin syringe:
- 100 units = 1.0 mL
- 50 units = 0.5 mL
- 10 units = 0.1 mL
- 1 unit = 0.01 mL
So when the calculator says “draw 20 units,” that means fill the syringe to the 20-unit mark. That’s 0.20 mL of liquid.
When to Ask Your Doctor
This calculator handles the reconstitution math, but dosing decisions should always involve your prescribing physician. Talk to your doctor before:
- Starting any new peptide
- Changing your dose
- Stacking multiple peptides (see our peptide stack guide)
- Experiencing side effects
Need a peptide prescription? Learn how to get peptides prescribed through telehealth or find a peptide clinic near you.
Frequently Asked Questions
How much bacteriostatic water should I add to my peptide vial?▼
The most common reconstitution volume is 2 mL, which makes the math easy. Some physicians prescribe 1 mL for more concentrated solutions (fewer injections from smaller syringes) or 3 mL for diluted solutions (easier to measure small doses precisely). Your pharmacy label should specify the volume.
Can I use sterile water instead of bacteriostatic water?▼
You can, but it’s not recommended. Bacteriostatic water contains 0.9% benzyl alcohol, which prevents bacterial growth in multi-use vials. Sterile water has no preservative — once opened, bacteria can grow. If you use sterile water, use the entire vial in one injection.
How do I know if my dose is too high or too low?▼
Start with the typical dose your physician prescribed. If you’re not seeing results after 4-6 weeks, talk to your doctor about adjusting. Signs of too-high dosing include water retention, tingling/numbness (GH peptides), nausea, or headaches. The calculator shows a warning if your entered dose falls outside the typical range.
How many doses can I get from one vial?▼
Divide the total peptide amount (in mcg) by your dose per injection. For a 5 mg (5,000 mcg) BPC-157 vial at 500 mcg per dose, that’s 10 doses. The calculator shows this automatically.
Is this calculator accurate for compounded peptides?▼
Yes. The math is the same regardless of the source. However, compounding pharmacies sometimes pre-reconstitute peptides or use different concentrations. Always check your pharmacy label first — if your peptide arrives already in liquid form, the concentration should be printed on the vial.
Sources
- Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev. 2018;6(1):45-53.
- White CM. A Review of the Pharmacologic and Pharmacokinetic Aspects of Synthetic Opioid Peptides. J Clin Pharmacol. 2022;62(2):158-167.
- United States Pharmacopeia. USP Chapter 797: Pharmaceutical Compounding — Sterile Preparations. 2023.
- Compounding Quality Act (DQSA), Section 503A. U.S. Food and Drug Administration. 2013.
- Walker RF. Sermorelin: A better approach to management of adult-onset growth hormone insufficiency? Clin Interv Aging. 2006;1(4):307-308.
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