Peptide Reconstitution Calculator: Dose and BAC Water
Calculate the exact BAC water volume to add, the insulin syringe units per dose, and how many doses your vial yields. Works for any lyophilized research peptide.
Quick presets
Click a peptide to load typical vial and starting dose. Adjust below.
Vial & dose inputs
Reconstitution result
Concentration
2.5 mg/mL
2500 mcg/mL
Volume per dose
0.1 mL
100 microlitres
Insulin syringe units
10 units
Draw to the 10-unit mark on a U-100 syringe
Doses per vial
20 doses
Approximate, assuming exact reconstitution
Units shown assume a U-100 insulin syringe where 1 unit = 0.01 mL. Always cross-check with your supplier's recommended reconstitution volume.
How to reconstitute a peptide vial
Lyophilized peptides arrive as a freeze-dried powder. To use them, you mix the powder with bacteriostatic water (BAC) inside the sealed vial. Once reconstituted, the peptide is stable in the fridge for 30 to 60 days depending on the compound.
- Wipe both rubber stoppers (peptide vial and BAC vial) with an alcohol swab and let dry.
- Use a 1 mL or 3 mL syringe with a draw needle to pull the BAC water volume calculated above out of the BAC vial.
- Insert the needle into the peptide vial at a slight angle so the water runs down the inside wall, not directly onto the powder. This minimizes foaming.
- Inject slowly. Do not shake the vial. Gently swirl until fully dissolved.
- Label the vial with reconstitution date and concentration in mg/mL.
- Refrigerate. Do not freeze a reconstituted vial.
For detailed shipping and storage handling and what to do if the vial arrived warm, see the peptide legality guide and the supplier shipping notes on each city guide.
Picking the right BAC volume
The amount of BAC water you add does not change the total amount of peptide in the vial. It only changes the concentration, and therefore how much volume you draw per dose. Common choices:
1 mL of BAC water
Most concentrated option. Good for high-mass vials (10mg+) where dose volumes would otherwise be hard to read. Lasts the same number of weeks.
2 mL of BAC water
The most common default. Strikes a balance between syringe readability and concentration. Standard for most GLP-1 reconstitutions.
3 mL of BAC water
Diluted. Useful for small doses (under 200 mcg) where a more spread-out reading on the syringe reduces measurement error.
The math is identical regardless of volume. The only practical difference is how precise your syringe reading is. If you find yourself trying to read 1 to 2 units on the syringe, dilute more. If you are drawing close to syringe capacity, concentrate more.
Reading the insulin syringe
Almost everyone in the peptide world uses U-100 insulin syringes for reconstituted peptides. The conversion is:
1 unit = 0.01 mL
100 units = 1 mL = full 1 mL syringe
So 25 units on the syringe is 0.25 mL of solution. The calculator above does this conversion automatically. If you ever see a result like "0.083 mL," convert to units (8.3 units) for easier reading.
Smaller syringe sizes (0.3 mL and 0.5 mL) have finer graduations and are easier to read for small doses. The 1 mL syringe gives you headroom for higher-dose protocols like tirzepatide maintenance phases.
Common reconstitution mistakes
Confusing mg and mcg
The single most dangerous mistake. A 250 mcg dose is 1000x smaller than a 250 mg dose. Always confirm the unit on your protocol before drawing. The calculator labels units explicitly to reduce this risk.
Shaking the vial
Shaking creates foam, which destabilizes the peptide. Gentle swirling is correct. If the powder does not dissolve immediately, give it a minute and swirl again.
Reconstituting with sterile saline instead of BAC water
Bacteriostatic water contains benzyl alcohol, which prevents bacterial growth once the vial is punctured. Sterile saline does not. A peptide reconstituted with saline must be used within hours, not weeks.
Freezing a reconstituted vial
Freezing breaks the peptide structure. Lyophilized (dry) peptide can be frozen pre-reconstitution. Once water is added, refrigerate only.
This is harm reduction education, not medical advice
This calculator is for educational use. Peptide protocols vary between individuals and compounds. Always cross-check with your protocol source, supplier instructions, and where possible a qualified clinician.