Insulin syringe units explained
Reviewed by the Rite Aid Health Team · Last updated July 2, 2026
Insulin syringes are marked in units, not millilitres. Here is how to read them and convert units to a dose.
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Units and the U-100 scale
Standard insulin syringes use the U-100 scale: 100 units equal 1 mL, so 1 unit is 0.01 mL. That scale is the same on every standard insulin syringe.
Barrel sizes
- 1 mL holds 100 units
- 0.5 mL holds 50 units
- 0.3 mL holds 30 units
- They are all U-100 — a smaller barrel just spaces small doses over more length, so they are easier to read.
Converting units to a dose
Units ÷ 100 gives the volume in mL. Multiply that by the concentration (mg/mL) to get the milligrams. The calculator does this for you from your vial size and water.
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For general education only — not medical advice or a treatment recommendation. Peptides are not a substitute for care from a licensed provider. Talk to a qualified healthcare professional before you start, stop, or change any peptide, medication, or supplement.
FAQ
On a U-100 insulin syringe, 1 unit is 0.01 mL. Ten units is 0.1 mL.
Pick by barrel size — 1 mL, 0.5 mL, or 0.3 mL. Smaller barrels make small doses easier to read. When unsure, use 1 mL.
25 units on a U-100 syringe.