How to Reconstitute Peptides: A Step-by-Step Guide

Lyophilized peptides arrive as a small puck of white powder at the bottom of a glass vial. To inject them, you have to dissolve that powder in bacteriostatic water — a sterile saline preserved with 0.9% benzyl alcohol that keeps the solution stable for ~30 days under refrigeration.

This guide walks through the exact process and the math so you never waste a dose.

What you'll need

• Lyophilized peptide vial (sealed)
• Bacteriostatic water (30 mL multi-dose vial is standard)
• One 3 mL drawing syringe with 21G needle (one-time use, for the bac water)
• Insulin syringes (U-100, 0.5 mL is fine for most peptides)
• Alcohol swabs
• A sharps container

Step 1 — Sanitize

Wipe both vial stoppers with an alcohol swab. Let them dry. Wash your hands.

Step 2 — Draw the bacteriostatic water

With the drawing syringe, pull air equal to the bac water you'll transfer (e.g., 2 mL). Invert the bac water vial, push the air in (this equalizes pressure), then draw 2 mL into the syringe.

Step 3 — Add water to the peptide vial slowly

Insert the needle, angle it so the water runs down the side of the vial wall. Push slowly. Do not blast water onto the lyophilized puck — this can denature the peptide.

Step 4 — Swirl, don't shake

Gently swirl the vial until the puck dissolves. Most peptides dissolve in under 30 seconds. If it doesn't dissolve, let it sit at room temperature for 5 minutes and swirl again.

Step 5 — Label and refrigerate

Label the vial with the reconstitution date. Refrigerate at 2–8°C. Most peptides are stable for ~30 days refrigerated. Some (like GHK-Cu) are light-sensitive — wrap them in foil.

The math, in one line

After reconstitution your vial has a known concentration:

mcg per mL  =  (vial mg × 1000) ÷ diluent mL

So a 5 mg BPC-157 vial reconstituted with 2 mL of bac water = 2,500 mcg/mL. On a U-100 syringe, 1 mL = 100 units, so 1 unit = 25 mcg. A 250 mcg dose = 10 units.

You can do this all in your head with practice, or just use the PeptideHub calculator.

Common mistakes

• Forcing water onto the puck. Always run it down the side wall.
• Shaking the vial. Some peptides denature; always swirl.
• Not labelling the date. A 30-day clock starts the moment you reconstitute.
• Using normal saline. Bac water is required for multi-dose vials. Saline has no preservative.
• Sharing needles. Insulin syringes are single-use only.

What about insulin syringes?

The cheapest, lowest-pain option is a U-100, 0.5 mL, 30G or 31G insulin syringe. The 0.5 mL barrel has clearer unit markings than a 1 mL syringe and is more than enough for most peptide doses.

Some research peptides (high-volume protocols like NAD+) need a 1 mL syringe or even a larger syringe with a smaller-gauge needle. The calculator flags this for you.

FAQ

Can I reconstitute with normal saline? Not if you plan to use the vial more than once. Saline has no preservative — bacteria grow. Use bacteriostatic water for any multi-dose vial.

How long do peptides last reconstituted? Most are stable ~30 days refrigerated. Some (semaglutide, BPC-157) last longer; some (light-sensitive ones like GHK-Cu) less. When in doubt, freeze a portion if you reconstitute more than you'll use in a month.

Should I filter the solution? No — filtration is for IV use. Subcutaneous and intramuscular peptide injections don't require filtering.

My vial is foamy / discolored. Cloudiness can indicate denaturation. Discoloration is almost always a sign to discard. Pink or yellow shouldn't appear in most peptides.

Next steps

• Open the calculator to compute exact draws for your peptide.
• Read How to choose a research peptide vendor before sourcing.
• Bookmark our peptide directory for dose ranges across 10+ compounds.