How to reconstitute peptides

How do you reconstitute a peptide vial, step by step?

Add a measured amount of bacteriostatic (bac) water or sterile water to the powder, swirl it gently until it dissolves, and check it's clear before you use it. These steps follow CDC injection safety guidance. They also follow the instructions for EGRIFTA SV and EGRIFTA WR, two FDA-approved peptides (tesamorelin) that patients mix at home from powder^1,3–4.

1. 1
   Wash your hands and clear a clean space

   Wash with soap and water, or use an alcohol-based hand rub, before you handle the vials^1,3. Work on a clean, dry surface.
2. 2
   Check both vials

   Read the labels on the peptide vial and the water. Bacteriostatic water contains 0.9% benzyl alcohol as a preservative and comes in a multiple-dose vial⁵. Check the expiry dates.
3. 3
   Wipe the rubber stoppers with alcohol

   Pop off the plastic caps and wipe the top of each vial with an alcohol swab. The CDC lists disinfecting the rubber stopper with alcohol before piercing it as a basic injection safety step¹. Let it dry and don't blow on it⁶.
4. 4
   Draw up the water with a new syringe

   Use a new, sterile needle and syringe every time you enter a vial¹. Draw exactly the amount of water you planned. If you haven't chosen an amount yet, the bac water guide explains how.
5. 5
   Add the water slowly down the side of the vial

   Tilt the needle slightly so the water runs down the inside wall of the vial, not straight onto the powder. Push the plunger slowly. The EGRIFTA SV instructions say this is to avoid foaming³.
6. 6
   Swirl or roll gently. Don't shake

   Roll the vial between your hands or swirl it in a small circle until the powder dissolves. Both tesamorelin labels say not to shake^3–4. Shaking and other stress can make peptides clump together (aggregate)⁷. If there's foam, let the vial sit until it settles⁴.
7. 7
   Check that it's clear

   The liquid should be clear and colorless with no particles. The tesamorelin labels say not to use it if it looks cloudy, discolored, or has particles in it^3–4.
8. 8
   Label the vial

   Write the date you mixed it and how much water you added. The CDC asks for multi-dose vials to be dated when first opened¹. You'll need the water amount every time you use the calculator, because it sets every dose from this vial.
9. 9
   Store it the way the label says

   Storage after mixing depends on the product. EGRIFTA SV must be used right away and not stored³. EGRIFTA WR is kept at room temperature and thrown away 7 days after mixing⁴. Research peptides have no label, so see how long reconstituted peptides last.

Peptide reconstitution formula: mg, mL and units

The peptide reconstitution formula is strength (mg/mL) = peptide in the vial (mg) ÷ water added (mL). On a U-100 insulin syringe, 100 units equal 1 mL, so 1 unit is 0.01 mL⁶. From there:

• mcg per unit = strength in mcg/mL ÷ 100
• units to draw = amount you want (mcg) ÷ mcg per unit
• mL to draw = units ÷ 100

1 mg = 1,000 mcg. Put everything in the same unit before you divide. Mixing up mg and mcg makes a dose 1,000 times too big or too small.

Worked example: 10 mg vial with 2 mL of bac water

A 10 mg peptide vial mixed with 2 mL of bac water is 5 mg/mL, or 5,000 mcg/mL. Each unit on a U-100 syringe then holds 50 mcg. These numbers show the math. They aren't a dose.

Common reconstitution mistakes that change the dose

The mistakes that change a dose most often are mixing up mg and mcg, using a U-40 syringe with U-100 math, and adding a different amount of water than you planned. Each one changes how much peptide is in every unit you draw.

• mg vs mcg. 500 mcg is 0.5 mg, not 500 mg. The safety group ISMP warns that the symbol "µg" gets misread as mg, and that a missing leading zero turns 0.5 mg into 5 mg⁸. Write "mcg" and always put a 0 before the decimal point.
• U-100 vs U-40 syringes. Some pet insulins, like Vetsulin, are U-40: 40 units per mL. Vetsulin's label says any syringe other than a U-40 syringe gives the wrong dose⁹. U-40 syringes are sold for those insulins, and the reverse is also true: peptide math on this site assumes U-100. Check for "U-100" on the syringe package. See how to read an insulin syringe.
• Wrong amount of water. Add 1 mL when you meant to add 2 mL, and every unit holds twice as much. You can't take water back out, so run the calculator with the amount you really added.
• Units mistaken for mL. ISMP reports errors where insulin units were mistaken for mL¹⁰. 10 units on a U-100 syringe is 0.1 mL, not 10 mL.

Bacteriostatic water or sterile water for reconstitution?

Approved peptide products use both, and the difference is the preservative. Bacteriostatic water is sterile water with 0.9% benzyl alcohol added to slow the growth of bacteria, and it comes in a multiple-dose vial⁵. Plain sterile water has no preservative. That's why approved products differ: EGRIFTA SV is mixed with sterile water and used at once³, while EGRIFTA WR is mixed with bacteriostatic water and used for 7 days⁴.

• The bac water label says it is not for use in newborns, because benzyl alcohol can be harmful to them⁵.
• The label says to use aseptic technique (keeping everything sterile) every time you enter the vial⁵.
• An opened multi-dose vial is usually dated and thrown away within 28 days unless the maker gives a different date^1–2,12. That rule covers the bac water bottle too.

For how much water to add, see how much bac water to add to a peptide vial.

Are research peptides approved for reconstitution and injection?

No. Peptides sold "for research use only" are not FDA-approved drugs, and they don't come with tested mixing or storage instructions. In an August 2026 warning letter to one seller, the FDA called its peptides unapproved new drugs, despite labels saying "for research use only"¹¹.

The steps on this page are general aseptic technique, the basics that apply to any vial. They can't tell you whether a product is pure, sterile or right for you. Check with a prescriber or pharmacist before you inject anything.