Reconstitution turns a freeze-dried peptide powder into an injectable solution. Get the math right and every dose lands where planned; get it wrong and you can be off by a factor of two. This article walks the chain — vial size to bacteriostatic water to mg/mL to insulin-syringe units — with worked examples for BPC-157, ipamorelin, HGH, and CJC-1295.
Reconstitution dissolves a lyophilized (freeze-dried) peptide powder in a sterile diluent so it can be drawn into a syringe and injected. Lyophilized peptides ship as dry powder because they are far more stable that way; once water is added, the resulting liquid has a defined concentration in milligrams per milliliter that drives every dosing calculation that follows.
FDA-approved peptide drugs work the same way. Somatropin formulations such as Humatrope and Genotropin ship as powder with a diluent cartridge. A 5 mg vial of BPC-157 or 2 mg vial of ipamorelin holds a fixed peptide mass; the injection volume is set entirely by how much bacteriostatic water you add. The label gives mass; the water volume gives concentration.
Bacteriostatic water is sterile water for injection containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits bacterial growth, which allows repeated draws from a multi-dose vial across many days. It is the standard diluent for reconstituting most lyophilized peptides and is used clinically with FDA-approved injectables such as somatropin and tesamorelin.
Plain sterile water for injection and 0.9% sodium chloride work for single-use reconstitution but lack antimicrobial properties for vials punctured repeatedly. The FDA label for Egrifta (tesamorelin) specifies sterile water for single-use reconstitution injected immediately; home users of research peptides reconstitute with bacteriostatic water so the vial lasts 28 to 30 days.
Concentration in milligrams per milliliter is simply the peptide vial size in milligrams divided by the volume of bacteriostatic water added in milliliters. A 5 mg BPC-157 vial reconstituted with 2 mL of bacteriostatic water yields a 2.5 mg/mL solution. This single number governs every dose-to-units calculation for that vial and does not change until the vial is empty.
Concentration (mg/mL) = Vial mass (mg) ÷ BAC water volume (mL)
Different water volumes shift the concentration: 5 mg + 1 mL = 5 mg/mL (small draws); 5 mg + 2 mL = 2.5 mg/mL (the common BPC-157 ratio); 5 mg + 5 mL = 1 mg/mL (easier syringe reads). None is wrong. Higher concentrations keep volumes small for larger doses; lower concentrations make small doses easier to measure — a 100 mcg dose at 1 mg/mL is 10 units on U-100.
On a U-100 insulin syringe, 100 units equal 1 mL, so 1 unit equals 0.01 mL. To convert a peptide dose into units: divide the target dose by the vial concentration to get volume in mL, then multiply by 100 to get units. A 250 mcg dose from a 2.5 mg/mL vial is 0.1 mL, which reads as 10 units on a U-100 syringe.
The full formula chain for any peptide:
1. Convert dose to mg if it is in mcg: dose_mg = dose_mcg ÷ 1000
2. Volume to inject (mL) = dose_mg ÷ concentration (mg/mL)
3. Units on U-100 = volume (mL) × 100
Two facts worth memorizing: 1 mL = 100 units on U-100, and 1 mg = 1000 mcg. Almost every reconstitution error traces back to confusing micrograms with milligrams, or assuming U-40 when you have U-100. The standard syringe sold in U.S. pharmacies is U-100, the global standard for human insulin per NIH StatPearls. Safety check: confirm the vial label, the dose in matching units, and the syringe reading before injecting.
The table below applies the formula chain to four common peptides at typical ratios. Each row shows vial size, water volume, concentration, a representative dose, and the matching U-100 draw.
| Peptide | Vial | BAC water | Concentration | Target dose | Volume | U-100 units |
|---|---|---|---|---|---|---|
| BPC-157 | 5 mg | 2 mL | 2.5 mg/mL | 250 mcg | 0.10 mL | 10 units |
| BPC-157 | 5 mg | 2 mL | 2.5 mg/mL | 500 mcg | 0.20 mL | 20 units |
| Ipamorelin | 2 mg | 2 mL | 1 mg/mL | 200 mcg | 0.20 mL | 20 units |
| Ipamorelin | 5 mg | 2 mL | 2.5 mg/mL | 300 mcg | 0.12 mL | 12 units |
| HGH (somatropin) | 10 mg (~30 IU) | 1 mL | 10 mg/mL (30 IU/mL) | 2 IU | ~0.067 mL | ~7 units |
| CJC-1295 (no DAC) | 2 mg | 2 mL | 1 mg/mL | 100 mcg | 0.10 mL | 10 units |
| CJC-1295 with DAC | 5 mg | 2.5 mL | 2 mg/mL | 2 mg (weekly) | 1.0 mL | 100 units |
The HGH row is worth noting. Somatropin is dosed in international units rather than milligrams, with roughly 3 IU per mg of recombinant somatropin, so a 10 mg vial contains about 30 IU. A 2 IU dose at 30 IU/mL is ~7 units on a U-100; performance-range doses of 4 to 6 IU draw to 13 to 20 units. The kinetics behind these compounds (somatropin half-life ~3.5 h, ipamorelin ~2 h, CJC-1295 with DAC ~8 days) are characterized in Teichman et al. 2006 for CJC-1295 and Raun et al. 1998 for ipamorelin.
Most reconstituted peptides remain stable for 28 to 30 days when stored refrigerated at 2 to 8°C (36 to 46°F) and shielded from light. Stability varies by compound: somatropin formulations such as Genotropin specify 21 to 28 day windows once reconstituted, while research peptides like BPC-157 and ipamorelin are commonly used within 30 days.
Three storage rules cover most cases. Refrigerate immediately and never freeze a reconstituted solution — freeze-thaw cycles cause fragmentation. Shield the vial from direct light. Do not shake vigorously; direct the BAC water down the inside wall and let the powder dissolve passively. CJC-1295 with DAC, somatropin, and tesamorelin should follow the shorter manufacturer window.
U-100 syringes are calibrated so that 100 units equal 1 mL; one unit is 0.01 mL. U-40 syringes calibrate 40 units per mL; one unit is 0.025 mL. U-100 is the global standard for human insulin and the default for peptide reconstitution math. U-40 is used primarily in veterinary medicine and is rarely encountered in human peptide protocols.
The danger is mismatched syringes: a U-100 protocol drawn on U-40 delivers 2.5x volume; the reverse under-delivers by the same factor. Verify the U-100 marking on the barrel before drawing. Standard U-100 peptide syringes are 0.3 mL (30 units) or 0.5 mL (50 units), with 8 mm or 12.7 mm needles for subcutaneous injection. The peptide-specific evidence base is summarized in Sikiric et al. (PMID 21443487) for BPC-157.
Dose Track’s built-in reconstitution calculator runs the full chain — vial mass, BAC water volume, concentration, dose, and U-100 units — every time you log a reconstitution or dose. It supports BPC-157, ipamorelin, somatropin, CJC-1295 with and without DAC, sermorelin, tesamorelin, TB-500, IGF-1 LR3, MOTS-c, SS-31, and 50+ other peptides. Vial expiration and remaining volume are tracked automatically. See the peptide tracking page or the full medications list, then download Dose Track on the App Store.