Complete Peptide Reconstitution Guide
Step-by-step instructions for safely reconstituting lyophilized peptides with bacteriostatic water.
What You'll Need
Lyophilized Peptide Vial
The sealed glass vial containing freeze-dried peptide powder. Check the label for compound name and amount (mg).
Bacteriostatic Water (BAC)
Sterile water preserved with 0.9% benzyl alcohol. Allows safe multi-use for up to 28 days. Available in 10 mL or 30 mL vials.
Insulin Syringes
29–31 gauge, 0.3 mL, 0.5 mL, or 1 mL. Use a fresh syringe for reconstitution and a new one for each dose.
Alcohol Swabs
70% isopropyl alcohol prep pads. Used to sanitize vial stoppers and injection sites.
Sharps Container
For safe disposal of used needles and syringes.
Step-by-Step Reconstitution
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Prepare Your Workspace
Clean a flat surface. Wash and dry your hands thoroughly, or wear disposable gloves. Gather all supplies before opening anything.
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Remove Vial Caps
Flip off the colored plastic caps from both the peptide vial and the bacteriostatic water vial, exposing the rubber stoppers underneath.
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Sanitize Stoppers
Wipe the rubber stopper of both vials with fresh alcohol swabs. Let them air dry for 10–15 seconds. Do not blow on them.
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Draw Bacteriostatic Water
Using a fresh insulin syringe, pull back the plunger to your desired volume of air (matching the BAC water amount). Insert the needle into the BAC water vial, inject the air (prevents negative pressure), then invert the vial and draw the calculated amount of water. Tap to remove air bubbles.
Use our Reconstitution Calculator to determine the exact volume.
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Add Water to Peptide Vial
Insert the syringe needle through the peptide vial's rubber stopper. Aim the needle tip against the glass wall — never spray directly onto the powder. Slowly depress the plunger, allowing water to trickle gently down the glass wall.
Critical: Inject slowly and against the wall. Spraying directly onto the powder causes foaming and can damage the peptide structure. -
Equalize Pressure
Before removing the syringe, lift the needle tip above the liquid level (but still under the stopper). Release the plunger slightly to allow pressure inside the vial to equalize. Then withdraw the needle.
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Dissolve Gently
Gently swirl the vial by rolling it between your palms. You can also tilt it slowly back and forth. Never shake vigorously. Most peptides dissolve within 1–3 minutes. If not fully dissolved, refrigerate for 15 minutes and try again.
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Label and Store
Label the vial with: compound name, concentration (mcg/mL), date reconstituted, and discard date (28 days). Refrigerate immediately at 2–8°C (36–46°F).
Understanding Concentration
After reconstitution, knowing your concentration is essential for accurate dosing.
Concentration (mcg/mL) = Peptide Amount (mg) × 1000 ÷ BAC Water Volume (mL)
Common Examples
| Vial | BAC Water | Concentration | 250 mcg dose = |
|---|---|---|---|
| 5 mg | 1 mL | 5,000 mcg/mL | 0.05 mL (5 units) |
| 5 mg | 2 mL | 2,500 mcg/mL | 0.10 mL (10 units) |
| 5 mg | 2.5 mL | 2,000 mcg/mL | 0.125 mL (12.5 units) |
| 10 mg | 2 mL | 5,000 mcg/mL | 0.05 mL (5 units) |
| 10 mg | 4 mL | 2,500 mcg/mL | 0.10 mL (10 units) |
| 2 mg | 1 mL | 2,000 mcg/mL | 0.125 mL (12.5 units) |
For precise calculations with your specific vial and dose, use our Reconstitution Calculator.
Drawing Your Dose
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Calculate Units
Volume (mL) = Desired Dose (mcg) ÷ Concentration (mcg/mL). Then multiply by 100 to get insulin syringe units.
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Sanitize
Alcohol-swab the vial stopper.
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Draw
Using a fresh syringe, draw to the calculated unit mark. Tap to remove bubbles. Inject slowly subcutaneously or as directed.
Troubleshooting
Peptide won't dissolve completely
Some peptides take longer to dissolve. Refrigerate for 15–30 minutes, then gently swirl again. If still not dissolved, ensure you're using the correct solvent. Hydrophobic peptides may require a small amount of DMSO or acetic acid before adding water — check your peptide's reconstitution notes.
Solution is cloudy or has particles
Slight cloudiness that clears with gentle swirling is normal. Persistent cloudiness or visible particles may indicate degradation or contamination. Discard and reconstitute a fresh vial.
Too much bacteriostatic water was added
Your concentration is now lower than intended. Recalculate: you'll need to draw a larger volume per dose. Update your vial label with the actual concentration.
Rubber bits fell into the solution (coring)
This happens when the needle punches through the stopper. Discard the vial — you cannot filter these out safely. To prevent coring, insert the needle at a slight angle and use a fresh needle each time.
Left reconstituted peptide out overnight
If at room temperature for more than a few hours, the peptide may have degraded. When in doubt, discard and reconstitute a new vial. Bacteriostatic water's preservative helps but doesn't replace refrigeration.