Peptide Reconstitution Calculator
Calculate how to reconstitute peptides with bacteriostatic water — get concentration, units to draw per injection, and total doses per vial.
Reconstituting peptides means mixing the freeze-dried powder with bacteriostatic water before injection. Use this calculator to figure out exactly how much water to add and how many units to draw on your insulin syringe.
Reconstitution Calculator
Fill in the details below to see exactly how to mix your peptide and how many units to draw.
Pick from the list or select 'Other' for a custom peptide
This is the amount of peptide powder in the vial. A common BPC-157 vial is 5 mg.
= 5,000 mcg of peptide
Most users add 2 ml. More water makes it easier to measure small doses.
If your peptide is dosed in mcg (like BPC-157), pick mcg. If it's dosed in mg (like Retatrutide or Semaglutide), pick mg.
= 0.25 mg
Mix your vial with 2 ml of bacteriostatic water
Inject the bac water slowly into the side of the vial. Swirl gently — don't shake.
Use a U-100 insulin syringe (1 ml size)
These are sold at pharmacies as 'insulin syringes'. The 1 ml size has 100 units marked on it.
Draw to 10 units for each dose
Pull the plunger back to the 10 mark on your insulin syringe.
You'll get 20 doses from this vial
Store the reconstituted vial in the fridge between 2–8°C. Most peptides last 2–4 weeks once mixed.
Draw the plunger back to here
Draw to: 10 units
Visual guide for a U-100 insulin syringe (100 units = 1 ml)
Show technical details (concentration, math)tap to expand
Concentration: 2500 mcg/ml
Math: 5mg ÷ 2ml = 2500 mcg/ml. 250mcg ÷ 2500mcg/ml × 100 = 10 units
What you'll need
All these are available from UK pharmacies and verified suppliers.
Bacteriostatic Water (10ml or 30ml vial)
Sterile water with 0.9% benzyl alcohol that prevents bacterial growth. You'll need ~2 ml per peptide vial.
Where to buy: Available from UK research chemical suppliers and some online pharmacies.
Browse suppliers →U-100 Insulin Syringes (0.5ml or 1ml)
Single-use insulin syringes with 100 unit markings. Use a fresh one for each injection.
Where to buy: Available from any UK pharmacy without prescription. BD Micro-Fine and Terumo are the most common brands.
Read injection guide →70% isopropyl alcohol pads. Use one to wipe the vial top before drawing each dose, and another to wipe your skin before injecting.
Where to buy: From pharmacies — cheap (£2-5 for 100).
A small puncture-proof container for safely disposing of used syringes. UK pharmacies will take full bins back for free disposal.
Where to buy: From pharmacies. Ask about the NHS sharps disposal scheme.
See our top insulin syringe picks
Independent rankings of the best UK syringes for peptide use.
Continue Your Research
Frequently Asked Questions
Common questions about reconstituting peptides and using insulin syringes.
How to Reconstitute Peptides
Add bacteriostatic water
Draw up the amount of bacteriostatic water shown above into a fresh insulin syringe. Inject slowly down the side of the vial — never directly onto the powder.
Allow to dissolve
Gently swirl the vial. Do not shake. Allow the peptide to dissolve completely. The solution should be clear.
Draw your dose
Using the units calculated above, draw your dose into a fresh insulin syringe. Store the reconstituted vial refrigerated and use within 28 days.
▶Show formula
Concentration: (Vial mg × 1,000) ÷ Water ml = mcg per ml
Units to draw: (Desired dose mcg ÷ Concentration mcg/ml) × 100 units
Doses per vial: (Vial mg × 1,000) ÷ Desired dose mcg
A standard U-100 insulin syringe contains 100 units per 1 ml.
Research use only. This calculator is provided for informational and research purposes only. Always verify calculations with a qualified healthcare professional before administration. PeptideGuide UK accepts no liability for decisions made based on this tool.