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How to Read a U-100 Insulin Syringe

On a U-100 syringe, 100 units = 1 mL, so 1 unit = 0.01 mL. The units measure volume — how much peptide that volume contains depends on how you mixed the vial.

The three common sizes

0.3 mL syringe — 30 units

Small marks usually every 1 unit
05101520253015 units0.3 mL · U-100 · 30 units

Shown filled to 15 units = 0.15 mL.

0.5 mL syringe — 50 units

Small marks usually every 1 unit
0510152025303540455025 units0.5 mL · U-100 · 50 units

Shown filled to 25 units = 0.25 mL.

1 mL syringe — 100 units

Small marks usually every 2 units
010203040506070809010050 units1 mL · U-100 · 100 units

Shown filled to 50 units = 0.5 mL.

Units vs mL vs mg

  • mL is volume. 1 mL = 100 units on a U-100 syringe.
  • Units are the marks on the syringe — also volume.
  • mg / mcg is the amount of peptide. To get from units to mg you need the concentration — use the units to mg converter.

Syringe FAQ

Which insulin syringe size should I use?

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Use the smallest syringe that holds your full dose. Smaller barrels have wider spacing between marks, so they are easier to read: a 0.3 mL syringe for doses up to 30 units, 0.5 mL up to 50 units, and 1 mL up to 100 units.

Are all insulin syringes U-100?

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Almost all insulin syringes sold in the US are U-100 (100 units per mL). U-40 and U-500 syringes exist for specific insulins and are marked differently. This site assumes U-100 throughout — check the label on the packaging.

What do the small marks between numbers mean?

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On most 0.3 mL and 0.5 mL syringes, each small mark is 1 unit (some 0.3 mL syringes have half-unit marks). On 1 mL syringes each small mark is usually 2 units. Count the marks between two numbers to be sure.