How much bacteriostatic water do I add to a 5 mg vial?

There is no single required volume; follow your pharmacy label or prescriber's instructions. Adding 1 mL gives a strength of 5 mg per mL, where a 250 mcg dose is 5 units; adding 2 mL gives 2.5 mg per mL, where 250 mcg is 10 units.

Does adding more water weaken the peptide?

No, adding more water only spreads the same milligrams across more liquid. Your dose in milligrams stays the same; you simply draw more syringe units to get that amount.

Can I use the reconstitution calculator for semaglutide?

Yes, enter your semaglutide vial milligrams, such as 5 mg or 10 mg, along with your water volume and prescribed dose. Our dedicated semaglutide calculator is another option for common semaglutide strengths.

Peptide reconstitution calculator

Find the syringe units to draw and the mixed vial strength in mg per mL, whether you use one peptide or a multi-peptide blend.

Only for reference. Your dose comes from your prescriber or the product label; this site just converts it into units.

on a U-100 syringe, in 1 unit: 0.01 mL
in a total of 100 units: 1 mL
in an amount of 1 mg: 1,000 micrograms

Once water is added, the peptide reconstitution calculator gives your vial's strength in mg per mL and the unit amount for each withdrawal. You can switch between syringes of 0.3 mL or 0.5 mL or 1 mL, and blend mode covers vials that hold more than 1 peptide. Your prescriber sets the dose; we handle the mixing and the volume math.

Reconstituting peptides of any vial size with the peptide reconstitution calculator

Dissolving dry powder in liquid is what reconstituting a peptide means; these calculations work for any vial weight and water volume. Your concentration comes from dividing vial mg by water mL. Mixing a 5 mg vial with 2 mL of water produces 2.5 mg per mL. A 30 mg tirzepatide vial mixed with 3 mL of water comes out at 10 mg per mL. Our guide to reconstituting peptides walks you through the mixing technique step by step.

What amount of water should you add?

More water spreads the peptide through a larger volume, which gives you more syringe units per dose and makes tiny doses easier to read. Fewer milliliters keep the liquid concentrated, which lets larger doses fit in 1 draw. However much water you add, the bottle still holds the same total milligrams. Try our water volume calculator for bacteriostatic water to select a volume that lines up with clear syringe marks. The CDC injection safety rules say to date a multi-dose vial and throw it away within 28 days after you puncture it.

A mixing calculator for peptide blends

Certain non-FDA-approved research vials hold 2 peptides in 1 bottle, like a BPC-157 and TB-500 blend at 10 mg or 20 mg. The same water volume dissolves both powders. Enter the label milligrams for each peptide, and you'll see how many mg of every ingredient each unit you draw contains. On our peptide stacking page, combined vials are compared with separate syringes.

Questions people ask

For a 5 mg vial, how much bacteriostatic water do I add?

No single volume is required; follow your pharmacy label or your prescriber's instructions. With 1 mL of water, the strength is 5 mg per mL; a 250 mcg dose measures 5 units. With 2 mL, it's 2.5 mg per mL; 250 mcg measures 10 units.

Will more water make the peptide weaker?

No; more water just spreads the same milligrams over more liquid. The milligrams in your dose stay the same; to reach that amount, you draw more syringe units.

Can semaglutide be used with the reconstitution calculator?

Yes, enter your semaglutide vial milligrams, for example 5 mg or 10 mg. Add your water volume and prescribed dose too. For common semaglutide strengths, our dedicated semaglutide calculator is another option.