Guides / How to read an insulin syringe
How to read an insulin syringe
2 min read
In short: Almost all insulin syringes are U-100: 100 units equals 1 mL, whatever the size. Smaller syringes have finer markings, so they are easier for small doses. Read the dose at the top edge of the plunger's rubber seal.
The three common sizes
| Syringe | Holds | Usual markings | Good for |
|---|---|---|---|
| 30 units | 0.3 mL | Every 1 unit (some every ½) | Small doses, finest reading |
| 50 units | 0.5 mL | Every 1 unit | Medium doses |
| 100 units | 1 mL | Every 2 units | Larger doses |
Markings vary by brand. Check the box, and count the lines between two numbers to see what each line is worth.
Where to read the dose
Look at the rubber seal at the end of the plunger. The edge closest to the needle is the one that lines up with the dose, not the tip of the cone or the far edge.
Getting rid of air bubbles
- With the needle pointing up, tap the barrel gently so bubbles rise.
- Push the plunger slightly to move the air out.
- Recheck that the seal still lines up with your dose, and adjust.
Units are not the same as IU
Syringe "units" are a volume (1/100 of a mL). "IU" (international units) is a measure of biological activity used for some medicines like HCG and growth hormone. They are completely different, and one can't be swapped for the other without the product's specific conversion.
Keep reading
Mixing a vial (reconstitution), step by step
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Injection sites and why rotation matters
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General information, not medical advice. Always follow your product's instructions and your healthcare professional.