The Complete Peptide Reconstitution Guide: Mixing Lyophilized Peptides Correctly
May 3, 2026 · Education
Most peptides arrive as a lyophilized powder — freeze-dried into a small puck at the bottom of the vial. Before you can inject anything, you need to mix it with a sterile solvent. This is reconstitution, and getting it right matters for both safety and dosing accuracy.
What you need
- Bacteriostatic water — sterile water with 0.9% benzyl alcohol added as a preservative. This is the standard solvent for most peptides. Once mixed, it stays good for ~28 days at fridge temp.
- Sterile saline (0.9% NaCl) — an isotonic alternative. Use this for peptides that sting on injection (GHK-Cu being the famous one). The matching tonicity reduces injection-site discomfort dramatically.
- Sterile (preservative-free) water — for peptides that will be used immediately or stored frozen.
- A 1 mL or 3 mL syringe with a 22-25 gauge needle for drawing solvent.
- Alcohol swabs.
Standard reconstitution volumes
Most peptide vials are sold in 5 mg or 10 mg sizes. Here are the common conversions:
| Vial size | Bac water added | Concentration | Result on a U-100 insulin syringe |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 10 units = 500 mcg |
| 5 mg | 2 mL | 2.5 mg/mL | 10 units = 250 mcg |
| 10 mg | 2 mL | 5 mg/mL | 10 units = 500 mcg |
| 10 mg | 5 mL | 2 mg/mL | 10 units = 200 mcg |
The “right” volume depends on your dose. Lower concentration = easier to draw small doses precisely.
Step-by-step technique
- Wipe both vial stoppers — bac water and peptide — with an alcohol swab. Let dry for 10 seconds.
- Draw your bac water into a syringe at the volume you calculated.
- Insert the needle into the peptide vial at a shallow angle so the bac water runs down the inside wall of the vial. Never squirt directly onto the lyophilized powder. The force destroys peptide bonds.
- Slowly press the plunger over 5-10 seconds.
- Swirl gently to dissolve. Do not shake. Shaking creates foam, denatures peptides, and reduces potency.
- Wait 30-60 seconds. If anything didn’t dissolve, swirl again. The solution should be clear.
- Label the vial with the date and final concentration. You’ll thank yourself in 3 weeks.
Storage after mixing
- Refrigerate at 2-8°C (38-46°F). The door is fine; the back of the fridge can occasionally freeze.
- Do not freeze reconstituted peptides. Ice crystals damage peptide bonds.
- Most peptides reconstituted in bac water are stable for 28 days. BPC-157 is shorter (14 days). Tirzepatide and Retatrutide are longer (30+ days).
- Protect from light. The original vial works fine, or use amber glass.
Common mistakes
- Shaking the vial. Always swirl. Foam = damaged peptides.
- Direct stream onto powder. Run the bac water down the side wall.
- Wrong solvent. Sterile water without bacteriostatic preservative is fine for same-day use, but won’t store. Plain tap water is never acceptable.
- Forgetting the math. Always recalculate when you change vial size or solvent volume.
- Mixing different peptides in the same vial. Don’t. Stability and potency interactions are unpredictable.
Disclaimer: Reference information only. Compounds sold for research use. Consult a healthcare provider familiar with peptide therapy before any administration.