How many units is 1 mL on an insulin syringe?

On a U-100 syringe, 1 mL is 100 units, so one unit is 0.01 mL. On a U-40 syringe, 1 mL is 40 units, so one unit is 0.025 mL. Almost every syringe sold for human use is U-100.

What is the difference between a 0.3 mL, 0.5 mL and 1 mL insulin syringe?

Only the total capacity. All three are U-100, so a unit means the same volume on each. A 0.3 mL barrel holds 30 units, a 0.5 mL holds 50, a 1 mL holds 100. The smaller barrel spreads those units over the same physical length, which makes small doses easier to read accurately.

How do I know if my syringe is U-100 or U-40?

It is printed on the barrel or the wrapper. U-40 syringes are usually veterinary and often have a red plunger. If you use a U-40 syringe with numbers worked out for U-100 you will draw two and a half times the intended dose.

What does 20 units mean in mL?

On a U-100 syringe, 20 units is 0.2 mL. The mass of peptide in that 0.2 mL depends entirely on how concentrated your vial is.

How to read an insulin syringe

Units are not a dose. They are a volume. Everything below follows from that one fact.

A unit is a volume, not an amount of drug

The numbers on an insulin syringe measure liquid, not medicine. On a U-100 syringe, which is what almost everything sold for human use is, 100 units is 1 mL. So one unit is 0.01 mL, twenty units is 0.2 mL, and fifty units is half a millilitre.

How much peptide is in that volume depends entirely on how concentrated your vial is, which is why nobody can answer "how many units should I take" without also knowing your vial strength and how much water you added.

The three sizes, drawn to scale

Here is the same 0.2 mL on all three common barrels. The liquid is identical in every row. Only the number you read changes, and only because the scale is stretched over a different length.

This is why a smaller barrel is better for a small dose. Twenty units occupies two thirds of a 0.3 mL syringe and one fifth of a 1 mL syringe, so the same misjudgement of a millimetre costs you far less on the small one.

The U-40 trap

A U-40 syringe holds 40 units in 1 mL, not 100. If you take a unit count worked out for a U-100 syringe and draw it on a U-40 barrel, you will take two and a half times what you intended. U-40 syringes are usually veterinary and often have a red plunger. Check the barrel before every draw.

Reading it accurately

Read at eye level, with the syringe vertical. Looking down at an angle shifts the apparent line.
Read the edge of the plunger stopper that faces the needle, not the middle of the rubber.
Flick out air bubbles before you read. A bubble means you drew less liquid than the mark says.
If your dose lands under about 5 units, reconstitute with more water so it lands somewhere readable. The dose does not change, only the volume it arrives in.

Work out your own number

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ReviewedDose ranges and half-life figures last checked 29 August 2026.

Free: The Protocol Pack, 25 printable pages. Including the part no other site writes down: what to do when you have already got it wrong. Wrong water volume, shook the vial, left it out overnight, drew the wrong units. Plus dosing cards for twelve compounds, titration planners and a vial log. Get it free.

Calculators by compound

RetatrutideVial, water and weekly dose to syringe units TirzepatideThe 2.5 to 15 mg ladder, converted SemaglutideThe 0.25 to 2.4 mg ladder, converted BPC-157mcg doses from a 5 or 10 mg vial ReconstitutionHow much water to add, and why it matters Dosing chartsPrintable unit tables for every compound Titration schedulesFull ladders with units at every step Reading a syringeU-100 vs U-40, and the 2.5x error How much water?Pick a volume that lands where you can read it

Common questions

How many units is 1 mL on an insulin syringe?: On a U-100 syringe, 1 mL is 100 units, so one unit is 0.01 mL. On a U-40 syringe, 1 mL is 40 units, so one unit is 0.025 mL. Almost every syringe sold for human use is U-100.
What is the difference between a 0.3 mL, 0.5 mL and 1 mL insulin syringe?: Only the total capacity. All three are U-100, so a unit means the same volume on each. A 0.3 mL barrel holds 30 units, a 0.5 mL holds 50, a 1 mL holds 100. The smaller barrel spreads those units over the same physical length, which makes small doses easier to read accurately.
How do I know if my syringe is U-100 or U-40?: It is printed on the barrel or the wrapper. U-40 syringes are usually veterinary and often have a red plunger. If you use a U-40 syringe with numbers worked out for U-100 you will draw two and a half times the intended dose.
What does 20 units mean in mL?: On a U-100 syringe, 20 units is 0.2 mL. The mass of peptide in that 0.2 mL depends entirely on how concentrated your vial is.

Read this before you use the numbers. This is a unit-conversion tool. It converts a vial strength and a volume of bacteriostatic water into a concentration, a draw volume and a mark on an insulin syringe. It does not tell you what to take, whether to take it, or whether a compound is safe for you. Most of the compounds listed here are sold for laboratory research use and are not approved for human use. Nothing on this site is medical advice. Dosing decisions belong with a licensed clinician who knows your history. Always confirm the strength printed on your own vial rather than trusting a preset.