This article is for educational and research purposes only. Nothing here constitutes medical advice. Dosing should only be determined by a licensed healthcare provider.
Why Reconstitution Math Matters
Peptides arrive as lyophilized (freeze-dried) powder. To use them, you dissolve the powder in bacteriostatic water — a process called reconstitution. The amount of water you add determines the concentration of the solution, which directly affects how much liquid you draw into the syringe for each dose. Getting this math wrong means getting your dose wrong, which can mean ineffective dosing or, worse, overdosing.
The Basic Formula
The core calculation is simple:
Concentration = Total peptide (mcg) ÷ Total water added (mL)
Then to find your draw volume:
Draw volume (mL) = Desired dose (mcg) ÷ Concentration (mcg/mL)
Worked Example 1: BPC-157
You have a 5 mg vial of BPC-157 and want to dose 250 mcg per injection.
- Step 1: Convert vial content to mcg: 5 mg = 5,000 mcg
- Step 2: Add 2 mL of bacteriostatic water
- Step 3: Calculate concentration: 5,000 mcg ÷ 2 mL = 2,500 mcg/mL
- Step 4: Calculate draw volume: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL
- Step 5: Convert to insulin syringe units: 0.1 mL = 10 units on a 100-unit syringe
- Result: Draw to the 10-unit mark for each 250 mcg dose. The vial contains 20 doses.
Worked Example 2: Ipamorelin
You have a 2 mg vial of Ipamorelin and want to dose 200 mcg per injection.
- Step 1: Convert: 2 mg = 2,000 mcg
- Step 2: Add 1 mL of bacteriostatic water
- Step 3: Concentration: 2,000 mcg ÷ 1 mL = 2,000 mcg/mL
- Step 4: Draw volume: 200 mcg ÷ 2,000 mcg/mL = 0.1 mL = 10 units
- Result: 10 units per dose, 10 doses per vial.
Choosing How Much Water to Add
You have flexibility in how much water to add. More water = more dilute solution = larger draw volumes (easier to measure small doses accurately). Less water = more concentrated = smaller draw volumes (but harder to measure precisely with standard insulin syringes). A good rule of thumb: choose a water volume that results in your target dose falling between 5-20 units on the syringe, where the graduation marks are easy to read.
Common Errors to Avoid
- Confusing mg and mcg: This is a 1,000x error. A dose of 250 mcg is 0.25 mg — not 250 mg.
- Confusing syringe units with dose units: "Units" on an insulin syringe are volume measurements (0.01 mL each), not dose measurements.
- Not labeling vials: After reconstitution, write the concentration on the vial. "2,500 mcg/mL" or "250 mcg per 10 units" prevents confusion later.
- Rounding errors: Use a calculator. Do not eyeball the math for injectable compounds.