What a 1 mL insulin syringe holds
A 1 mL insulin syringe holds 100 units of U-100 insulin, the largest of the three common sizes (the others hold 30 and 50 units).[1] U-100 insulin has 100 units in each mL, so the full barrel is exactly 1 mL.[2] “100 unit” describes the capacity; “U-100” describes the scale. A 0.3 mL syringe is also a U-100 syringe, but it holds only 30 units.
1 mL syringes also exist on the U-40 scale, where the same barrel holds 40 units, so read the scale printed on the barrel. Under ISO 8537, embecta uses an orange needle shield for U-100 and red for U-40.[3]
1-unit or 2-unit lines
embecta makes 1 mL syringes with either a 1-unit or a 2-unit scale, and its own example of a 1 mL barrel is labelled “each line is 2 units”.[3] To find out which you have, count the small spaces between two numbered lines: if 10 units span 5 spaces, each line is 2 units; if they span 10, each line is 1 unit.
25 units on a 2-unit scale: halfway between the 24 and 26 lines
25 units on a 1-unit scale: on its own line
5, 10, 25 and 50 units on a 100 unit syringe
On a 100 unit syringe, 5 units is 0.05 mL, 10 units is 0.1 mL, 25 units is 0.25 mL and 50 units is 0.5 mL. Line up the thin black line on the plunger with the mark.[4]
5 units · 0.05 mL
10 units · 0.1 mL
50 units · 0.5 mL
| Reading | mL | Small lines from 0 (1-unit scale) | Small lines from 0 (2-unit scale) |
|---|---|---|---|
| 2 units | 0.02 | 2 | 1 |
| 5 units | 0.05 | 5 | 2.5 (between lines) |
| 10 units | 0.1 | 10 | 5 |
| 15 units | 0.15 | 15 | 7.5 (between lines) |
| 20 units | 0.2 | 20 | 10 |
| 25 units | 0.25 | 25 | 12.5 (between lines) |
| 30 units | 0.3 | 30 | 15 |
| 40 units | 0.4 | 40 | 20 |
| 50 units | 0.5 | 50 | 25 |
| 60 units | 0.6 | 60 | 30 |
| 75 units | 0.75 | 75 | 37.5 (between lines) |
| 80 units | 0.8 | 80 | 40 |
| 100 units | 1 | 100 | 50 |
U-100 insulin syringe sizes: when 1 mL is the right barrel
Of the common U-100 sizes, only the 1 mL syringe holds more than 50 units.[1] For smaller amounts, the 0.3 mL and 0.5 mL barrels are marked in 1-unit lines, and ½-unit lines are available on 0.3 mL barrels.[3] Which syringe to use is your prescriber's or pharmacist's decision. The full comparison is in insulin syringe sizes.
Volumes over 1 mL need a syringe marked in mL, which BD makes in 1 mL and larger sizes.[5] To convert any reading, use mL to units; to practise reading, try the trainer in how to read insulin syringe units; for what an insulin syringe is in general, see insulin syringe.
Frequently asked questions
How many mL is a 100 unit insulin syringe?
1 mL. On the U-100 scale, 100 units equal 1 mL.
How do you read 10 units on a 1 mL insulin syringe?
Line up the plunger with the line marked 10. On a 2-unit scale that is the fifth small line after 0; on a 1-unit scale it is the tenth.
Where is 25 units on a 1 mL insulin syringe?
On a 1-unit scale, on its own line. On a 2-unit scale, halfway between the 24 and 26 lines. 25 units is 0.25 mL.
Is a 100 unit syringe the same as a U-100 syringe?
A 100 unit syringe is a U-100 syringe, but not every U-100 syringe holds 100 units: the 0.3 and 0.5 mL sizes hold 30 and 50.