Reconstitution guide
How to turn a vial of powder into an accurate dose: what to mix it with, how much to add, how to mix it without damaging it, and how to read the syringe.
Know your vial
- Flip-off cap
Pop it off. The stopper underneath isn’t sterile.
- Rubber stopper
Wipe it with an alcohol swab and let it dry before every puncture.
- Headspace
Often sealed under vacuum, so it pulls water in. Keep a grip on the plunger and let the water run down the glass.
- Label
After mixing, write the date, the water added and the strength in mg/mL. The calculator writes this line for you.
- Lyophilized cake
The peptide, freeze-dried. Water goes down the wall, not onto the cake.
- Glass
Swirl or roll until the solution is clear. Never shake.
What you need
- The peptide vial (freeze-dried powder, also called lyophilized)
- A diluent, usually bacteriostatic water (see the table below)
- Alcohol swabs
- A 1 to 3 mL syringe to add the water
- U-100 insulin syringes to measure doses
- A sharps container
| Diluent | What it is | When it’s used |
|---|---|---|
| Bacteriostatic water | Sterile water with 0.9% benzyl alcohol, which keeps bacteria from growing after the stopper is punctured. | Multi-dose vials. The default for most peptides. |
| Sterile water | Sterile water with no preservative. | Single-use mixing that’s used right away (Egrifta SV’s label, for example). |
| 0.9% sodium chloride | Sterile saline. | When a label calls for it (Thymalin, for example). |
| 0.6% acetic acid | Dilute acid. | IGF-1 LR3, per its maker, to keep it from sticking to surfaces. It stings. |
Choose how much water
Water doesn’t change the dose. It only changes how much liquid carries it. More water makes a weaker solution, so each dose takes up more room in the syringe. That makes small doses easier to measure, but the injection gets larger. A good target is a volume that puts your usual dose between about 5 and 50 units.
| Water in a 5 mg vial | Strength | A 250 mcg dose | Volume |
|---|---|---|---|
| 1 mL | 5 mg/mL | 5 units | 0.05 mL |
| 2 mL | 2.5 mg/mL | 10 units | 0.10 mL |
| 2.5 mL | 2 mg/mL | 12.5 units | 0.13 mL |
| 3 mL | 1.667 mg/mL | 15 units | 0.15 mL |
volume (mL) = dose (mcg) ÷ strength
units = volume × 100 (on a U-100 syringe)
Worked example: 5 mg + 2 mL = 2,500 mcg/mL. 250 mcg ÷ 2,500 = 0.10 mL, which is 10 units.
Mixing, step by step
- PrepareWash your hands and clean the work surface. Let a refrigerated or frozen vial come to room temperature.
- Clean the stoppersFlip off the plastic caps and wipe both rubber stoppers with an alcohol swab. Let them air-dry.
- Draw the waterPull the planned amount of bacteriostatic water into the mixing syringe.
- Add it slowlyPush the needle through the peptide vial’s stopper and angle it so the water runs down the inside wall. Don’t spray it onto the powder.
- Swirl, don’t shakeGently swirl or roll the vial until the powder dissolves. Shaking foams the solution and can break down some peptides.
- Check itThe solution should be clear (copper blends are clear blue). Don’t use it if it’s cloudy, has particles or has changed color.
- Label itWrite the date, the water added and the strength (mg per mL) on the vial. The calculator writes this line for you.
- RefrigerateStore it at 2 to 8 °C, away from light. Never freeze a mixed vial.
Reading an insulin syringe
U-100 means 100 units equals 1 mL, so on any U-100 syringe 1 unit is 0.01 mL. The sizes differ only in how much they hold and how far apart the lines are.
0.3 mL, 30 units
One line is 1 unit. The easiest to read for doses under 30 units.
0.5 mL, 50 units
One line is 1 unit.
1 mL, 100 units
One line is 2 units, so odd numbers fall between lines.
- Read the dose at the edge of the black stopper nearest the needle.
- Tap out air bubbles before you read it. Bubbles take up space and shrink the dose.
- Use U-100 syringes with the numbers on this site. U-40 syringes, sold for some pet insulins, are marked differently.
Storage and shelf life
| State | Where | How long |
|---|---|---|
| Sealed powder | Freezer (−20 °C) for long-term storage; fridge for shorter periods. Keep it dark and dry. | Months to years, depending on the compound. |
| Mixed with bacteriostatic water | Fridge, 2 to 8 °C, away from light. Never freeze. | Most guides use about 3 to 4 weeks. Multi-dose vials are typically discarded 28 days after the first puncture (USP 797). |
| Mixed with sterile water | Fridge. | Single use, because there’s no preservative. |
| Label exceptions | Per the label. | Glutathione (TAD label): within 8 hours. Egrifta SV: right away. |
Common mistakes
- Mixing up mg and mcg. 1 mg is 1,000 mcg, so 0.25 mg is 250 mcg.
- Reading units as mL. 10 units is 0.10 mL, not 10 mL. FDA reported 5 to 20 times overdoses from this with compounded semaglutide.
- Not recalculating. A different amount of water changes the units for every dose.
- Using the wrong syringe scale. U-40 and U-100 syringes are marked differently.
- Treating a blend like a single peptide. Every unit of a blend contains all of its peptides in a fixed ratio.
Troubleshooting
Many vials are sealed under vacuum. Keep a steady grip on the plunger so the water enters slowly and runs down the wall.
Tilt and slowly roll the vial so the solution washes it down.
Let the vial rest in the fridge and the bubbles will settle. Shaking causes this, so swirl next time.
Give it 5 to 10 minutes with gentle rolling. Some compounds, like the small molecule SLU-PP-332, dissolve poorly in water. If it stays cloudy, don’t use it.
Discard it.