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 | 200 mcg | 250 mcg | 300 mcg |
|---|---|---|---|---|
| 5 mg vial + 1 mL water | 5 mg/mL | 4 u | 5 u | 6 u |
| 5 mg vial + 2 mL water | 2.5 mg/mL | 8 u | 10 u | 12 u |
| 5 mg vial + 3 mL water | 1.66667 mg/mL | 12 u | 15 u | 18 u |
| 5 mg vial + 5 mL water | 1 mg/mL | 20 u | 25 u | 30 u |
| 10 mg vial + 1 mL water | 10 mg/mL | 2 u | 2 u | 3 u |
| 10 mg vial + 2 mL water | 5 mg/mL | 4 u | 5 u | 6 u |
| 10 mg vial + 3 mL water | 3.33333 mg/mL | 6 u | 8 u | 9 u |
| 10 mg vial + 5 mL water | 2 mg/mL | 10 u | 12 u | 15 u |
| 50 mg vial + 1 mL water | 50 mg/mL | 0 u | 0 u | 1 u |
| 50 mg vial + 2 mL water | 25 mg/mL | 1 u | 1 u | 1 u |
| 50 mg vial + 3 mL water | 16.6667 mg/mL | 1 u | 2 u | 2 u |
| 50 mg vial + 5 mL water | 10 mg/mL | 2 u | 2 u | 3 u |
Worked example: a 5 mg vial with 2 mL of bacteriostatic water is 2.5 mg/mL. A 250 mcg draw is 0.10 mL, which is 10 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 5 mg vial with 2 mL of water is 2.5 mg/mL, so 250 mcg = 0.1 mL = 10 units. A 50 mg vial with 5 mL is 10 mg/mL, so the same 250 mcg is only 2.5 units — too small to measure well, which is why large vials get more water or a smaller draw.
The copper. GHK-Cu is a copper complex, and a clear blue solution is normal; cloudiness or particles are not.
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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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