Guide
Reconstitution, step by step
Every number in the calculator follows from three inputs: how much compound is in the vial, how much liquid you add and how much you want to measure out.
1. Work out the concentration
Convert the vial content from milligrams to micrograms by multiplying by 1,000, then divide by the volume of bacteriostatic water in mL. A 10 mg vial with 2 mL of water holds 10,000 ÷ 2 = 5,000 mcg/mL. A 5 mg vial with 2.5 mL holds 2,000 mcg/mL.
2. Work out the volume
Divide the amount you want by the concentration. 250 mcg at 5,000 mcg/mL is 250 ÷ 5,000 = 0.05 mL. If the amount is in mg, multiply by 1,000 first.
3. Convert mL to U-100 units
On a U-100 syringe, 1 mL equals 100 units, so multiply the volume in mL by 100. 0.05 mL reads as 5 units. The 0.3 mL, 0.5 mL and 1.0 mL sizes all use this scale; a 0.3 mL barrel holds 30 units, a 0.5 mL barrel 50 and a 1.0 mL barrel 100.
4. Count the measures in the vial
Divide the total micrograms in the vial by the amount per measure and round down. 10,000 mcg ÷ 250 mcg = 40 whole measures. In practice a little liquid stays in the vial and the needle hub, so the usable count is often slightly lower.
Choosing a water volume
The water volume changes the concentration, not the amount of compound. More water makes a weaker solution and a larger volume to measure, which is easier to read on a syringe. Less water makes a stronger solution and a smaller volume. Aim for volumes that land well above 2 units and below the capacity of the syringe you have. If the calculator says a volume won't fit, choose a larger syringe or plan a smaller water volume before you reconstitute.
Why there is no fixed mg to mL conversion
Milligrams measure mass and milliliters measure volume. The link between them is the concentration you create. Once you know it, mL = mcg ÷ (mcg per mL).
Good laboratory technique
- Let a refrigerated vial reach room temperature before opening to limit condensation.
- Wipe the rubber stopper with an alcohol swab and let it dry.
- Add the water slowly down the inside wall of the vial rather than directly onto the powder.
- Swirl or roll gently until dissolved. Shaking can cause foaming and may damage some peptides.
- Label the vial with the compound, concentration and date of reconstitution.
- Store the solution refrigerated and use a fresh sterile needle for every draw.
Quick unit reference
| Value | Equals |
|---|---|
| 1 mg | 1,000 mcg |
| 1 g | 1,000 mg |
| 1 mL | 100 units on a U-100 syringe |
| 0.5 mL | 50 units |
| 0.3 mL | 30 units |
| 0.1 mL | 10 units |
| 1 unit | 0.01 mL |
Check the label and the certificate of analysis
The vial label states the nominal content. A batch certificate of analysis shows identity, purity and sometimes the measured net peptide content, which can be lower than the gross powder weight because peptides carry water and salt counter-ions. For exact work, base your calculation on the verified content.