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Calculator/Insulin

Medication

Insulin syringe calculator

Insulin is the one medication the insulin syringe was built for. As long as the U on the vial matches the U on the syringe, the mark is the dose. This page is about what happens when they do not match.

Dose to syringe mark calculator

Which insulin vial do you have?Read the box or the label

U-100 insulin
units/mL
U-40 veterinary insulin
units/mL
Arithmetic only, not a dose recommendation. This converts the numbers you typed and nothing more. If anything here does not match your prescription or your label, stop and ask your pharmacist.
Full notice

This tool does not choose or check a medication, dose, concentration, diluent, syringe or route. It works from the numbers on your prescription and label, as you type them. A mark on a U-100 syringe is a volume, not a medication dose in units or IU. If anything here differs from what you were given, or you are unsure, do not prepare or inject: ask the prescriber or the dispensing pharmacist. No preset is a dose. Presets exist for FDA-approved products; any other vial is arithmetic on your own label.

  • Arithmetic: checked against 24 worked examples, last run 2026-09-05. See the examples
  • Vial presets: read from current FDA labels, checked 2026-09-04. Sources
  • Clinical review: none. No clinician reviews this site; the presets are read from the labels above and the result is arithmetic. Confirm every draw with your pharmacist.
  • Report a problem

The match, and the ways it breaks

A U-100 syringe is marked so that one mark holds one unit of U-100 insulin. That is the whole design: 100 units per millilitre in the vial, 100 marks per millilitre on the barrel, so 10 units is the 10 mark and nobody needs a calculator. The three things on this page all break that match. Veterinary insulin is U-40 and needs a U-40 syringe. Humulin R U-500 is five times as strong and needs its own syringe, and its label says not to convert. And when an insulin syringe is used for a medication that is not insulin, the marks go back to being plain volume.

Check the official label

Insulin lispro label on DailyMedVetsulin label on DailyMedProZinc label on DailyMedHumulin R U-500 label on DailyMed

Every number this page uses was read from these documents on 2026-09-04. The label is the authority; if it disagrees with this page, the label wins.

What the labels say

U-100 vials100 units per mL. On a U-100 syringe, the mark equals the dose.
U-40 veterinaryVetsulin and ProZinc, 40 units per mL. The label requires a U-40 syringe.
U-500 concentratedHumulin R U-500 needs its own syringe; its label says no conversion. Not offered here.
Pens, U-200, U-300Deliver their own measured dose. Not drawn with a syringe.

The wrong U

The wrong U on the syringe. U-40 and U-100 syringes are the same size and shape. U-100 insulin drawn to the 10 mark on a U-40 syringe is 25 units, two and a half times the dose. U-40 insulin drawn to the 10 mark on a U-100 syringe is 4 units. The U number is printed on the box and on the barrel; read both, every time, because the two boxes can sit side by side in the same drawer.

The calculator will not let a U-40 preset be paired with a U-100 syringe or the reverse. If it refuses your combination, that is the check working. The question for the pharmacy, if the boxes do not match: "This insulin is U-40 and these syringes are U-100. Which one is wrong?"

Reading the three sizes

All U-100 syringes share one scale. They differ in how far it goes and how finely it is marked, which is why a small dose is easier to read on a small syringe. Pick a size in the calculator and the drawing changes to match.

SyringeReadsMarksWhere 25 units sits
1 mL0 to 100Every 2; numbers every 10Halfway between the 24 and 26 ticks
0.5 mL0 to 50Every 1; numbers every 5On the 25
0.3 mL0 to 30Every half unit on many brandsOn the 25

A half-unit dose can only be read on a syringe with half-unit marks. The calculator rounds to the smallest mark on the syringe you chose and tells you when it has.

Worked answers

0.3 mL is how many units on an insulin syringe?0.5 mL is how many units on an insulin syringe?1 mL is how many units on an insulin syringe?How many mL is 10 units on an insulin syringe?How many mL is 50 units on an insulin syringe?How many units is 2.5 mg on an insulin syringe?How many units is 5 mg on an insulin syringe?Units to mL chartAny concentration chart

Two more questions

I use an insulin syringe for a medication that is not insulin. Do the units still apply?

The marks still measure volume, a hundredth of a millilitre each, but they no longer equal your dose. "10 units" does not identify a tirzepatide dose without the vial concentration; 0.1 mL of a stated concentration does. Convert through the concentration on your vial with the main calculator.

My vet prescribed units for my pet. Which syringe?

The one the insulin label names. Vetsulin and ProZinc are U-40 and require U-40 syringes. Some vets prescribe U-100 human insulin for animals, and that needs U-100 syringes. The box of syringes should carry the same U as the box of insulin.