Published by Peptide Protocols · Reviewed September 2026 · How we make these pages · Educational & research purposes only — not medical advice.
1 mL = 100 units on a U-100 insulin syringe. Formula: mg ÷ mL = mg/mL; (mcg ÷ 1000) ÷ mg/mL = mL; mL × 100 = units.
Units to draw on a U-100 insulin syringe for the common vial sizes and water volumes. Pick the row that matches your vial and the water you added.
| Vial + water | Concentration | 100 mcg | 200 mcg | 500 mcg |
|---|---|---|---|---|
| 2 mg vial + 1 mL water | 2 mg/mL | 5 u | 10 u | 25 u |
| 2 mg vial + 2 mL water | 1 mg/mL | 10 u | 20 u | 50 u |
| 2 mg vial + 3 mL water | 0.666667 mg/mL | 15 u | 30 u | 75 u |
| 3 mg vial + 1 mL water | 3 mg/mL | 3 u | 7 u | 17 u |
| 3 mg vial + 2 mL water | 1.5 mg/mL | 7 u | 13 u | 33 u |
| 3 mg vial + 3 mL water | 1 mg/mL | 10 u | 20 u | 50 u |
| 5 mg vial + 1 mL water | 5 mg/mL | 2 u | 4 u | 10 u |
| 5 mg vial + 2 mL water | 2.5 mg/mL | 4 u | 8 u | 20 u |
| 5 mg vial + 3 mL water | 1.66667 mg/mL | 6 u | 12 u | 30 u |
Worked example: a 3 mg vial with 2 mL of bacteriostatic water is 1.5 mg/mL. A 200 mcg draw is 0.13 mL, which is 13 units. Change the water and every number on the syringe changes — which is the single most common reconstitution mistake. The full explanation is in How to Reconstitute Peptides.
A 3 mg vial with 2 mL of water is 1.5 mg/mL, so 200 mcg = 0.13 mL = 13 units. A 5 mg vial with 2 mL (2.5 mg/mL) puts 200 mcg on 8 units; a 2 mg vial with 1 mL (2 mg/mL) on 10 units.
For a 3 mg vial, 1 mL gives 3 mg/mL (200 mcg = 7 units, hard to read); 2 mL gives 1.5 mg/mL (13 units); 3 mL gives 1 mg/mL (20 units, the easiest line). Choose the volume that makes your draw land on a readable line.
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The one formula, a BAC-water chart, and the 10 most-researched beginner peptides — the math done for you. Print it for the fridge.
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