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.

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

Products with this specification

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

Last edited . Equipment only: nothing on this page is advice about what to inject, how much, or whether a product is fit to use. That comes from the product's labelling and whoever supplied it. Product pages link to your own country's Amazon store through affiliate links; your price is the same.