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What does U-100 mean?
Insulin syringes are marked in units instead of millilitres. On any standard U-100 syringe, 100 units = 1 mL, so 10 units is 0.1 mL — the same on every barrel size. Full explanation →
Why it matters when you shop
U-100 is the scale on an insulin syringe: 100 units to the millilitre, so one unit is 0.01 mL. It is a measure of liquid volume, not of anything dissolved in it. The other scale, U-40, exists for animals and reads two and a half times differently; a U-40 syringe bought by mistake is the classic measuring error.
What to look for on the listing
- "U-100" printed on the barrel and in the listing title.
- The capacity in mL beside it: 0.3, 0.5 or 1 mL, which sets how many units fit (30, 50, 100).
- The marking step: 1 unit on the small barrels, 2 units on most 1 mL barrels, half units on the special ones.
Go deeper
- Guide: Insulin syringe units to mL: the quick conversion
- Comparison: 0 3 Vs 0 5 Ml Insulin Syringes
- Tool: Product Finder for this category
- All terms: the glossary
Products where this number appears
Insulin Syringes 31G, 0.5 mL Markings: U-100Insulin Syringes 31G, 0.3 mL Markings: U-100Insulin Syringes 30G, 1 mL Markings: U-100Half-Unit Insulin Syringes, 0.3 mL Markings: U-100Luer-Lock Syringes, 3 mL Markings: mL10 mL Luer-Lock Syringes Markings: mL
Reviewed 2026-09-03. Definitions describe equipment, not treatment. Affiliate links open your own country's Amazon store; your price is the same.