Insulin Syringe Conversion Chart

Read the barrel before you read the vial. A syringe unit is a volume, not a dose: on a U-100 barrel one unit is 0.01 mL and nothing else, and how many milligrams that delivers depends entirely on the concentration printed on the vial. The first two tables take you from units to milligrams at the strengths this site covers; the third goes the other way, from a volume you were told to draw back to the mark you set the plunger to.

U-100 is not a brand or a size — it is the scale. It means the barrel is graduated so 100 units equals exactly 1 mL, which is why a 1 mL insulin syringe is numbered to 100, a 0.5 mL to 50 and a 0.3 mL to 30. All three read in the same units; they differ only in how far apart the marks are printed.

If the barrel is marked U-40 instead, every number on it means something different. U-40 is the veterinary scale, 40 units to the millilitre, so a "20 units" instruction drawn on a U-40 barrel delivers 0.5 mL where a U-100 barrel would have delivered 0.2 mL — 2.5 times the intended dose. The fourth table is that error in full. Check the scale printed on the barrel and on the box; do not go by the needle, the colour of the cap or the size of the syringe.

Units to millilitres and milligrams — reconstituted peptides

Left column is the mark you set the plunger to on a U-100 barrel. Concentration is what your vial works out to after reconstitution — vial mass divided by the bacteriostatic water added.

Peptide doses are usually written in micrograms. At 1 mg/mL one unit mark delivers 10 mcg, at 5 mg/mL it delivers 50 mcg and at 10 mg/mL it delivers 100 mcg — multiply any milligram figure above by 1,000.

Units to milligrams — oil solutions

The same barrel marks at the strengths testosterone and other oil-based injectables are supplied in. The volume is unchanged; only what is dissolved in it differs.

Oil is drawn through a wider needle than an insulin syringe carries, and the labelled route for testosterone in oil is intramuscular. This table converts the number, not the method.

Millilitres to units, and which barrel holds it

Going the other way: a volume in millilitres, the mark it corresponds to on each scale, and whether the barrel in your hand can take it in one draw.

The two unit columns are the same physical volume expressed on two different scales. They are never interchangeable — read the second column only to recognise a U-40 barrel, never to dose from one unless the medicine is itself U-40.

U-40 barrels: the 2.5× error

Everything on this site is written for U-100. If a U-100 instruction is drawn on a U-40 barrel, the plunger stops at the right number and the wrong volume. This table is what that costs. It is not a dosing table — no figure in the U-40 column is a dose to give.

A U-40 barrel is numbered only to 40, so any U-100 instruction above 40 units cannot be drawn on one at all — the one case where this mistake catches itself. Below that it is silent. U-40 insulin is not a human strength in the United States; the FDA-approved U-40 product is veterinary.

Which barrel, and what one mark is worth

All three insulin barrel sizes read in units, so the same instruction can be drawn on any of them. What differs is how far apart the marks are printed, which is what decides the smallest dose you can set with confidence.

The half-unit scale is stated by the manufacturer only for the 0.3 mL barrel — embecta: "Designed with large dose unit markings, with ½ unit scale marking available on the 0.3mL barrel" — and FDA device listings carry 0.3 mL models named for it. We could not find a manufacturer instruction-for-use or FDA listing that states the printed graduation interval on a 0.5 mL or 1 mL barrel, so this chart does not state one. Hold your own barrel up and count the lines between two numbers before you draw a small dose on it.

Frequently asked questions

How many units is 0.5 mL on an insulin syringe?

On a U-100 syringe, 0.5 mL is 50 units — the conversion is fixed, because U-100 means 100 units to the millilitre. It fills a 0.5 mL barrel exactly and reaches the halfway mark on a 1 mL barrel. On a U-40 veterinary barrel the same 0.5 mL is 20 units, which is why the two scales must never be mixed.

How many mL is 10 units?

0.1 mL on a U-100 syringe, and 0.25 mL on a U-40 one. The volume says nothing about the dose on its own: 0.1 mL is 0.5 mg from a 5 mg/mL peptide vial and 20 mg from a 200 mg/mL oil vial.

How do I convert syringe units to milligrams?

Divide the units by 100 to get millilitres, then multiply by the concentration in mg/mL. Twenty units is 0.2 mL, which is 0.4 mg at 2 mg/mL, 2 mg at 10 mg/mL and 40 mg at 200 mg/mL. One unit mark is worth one hundredth of whatever is in a millilitre.

What is the difference between a U-40 and a U-100 syringe?

The scale printed on the barrel. U-100 is graduated at 100 units per millilitre, U-40 at 40 — so one U-40 unit mark is 0.025 mL against 0.01 mL on a U-100, and drawing a U-100 instruction on a U-40 barrel delivers 2.5 times the intended dose. U-40 is the veterinary scale: the FDA-approved U-40 insulin, Vetsulin, states "U-40 insulin contains 40 units/mL (1 mL = 1 cc)" and warns that "USE OF A SYRINGE OTHER THAN A U-40 SYRINGE WILL RESULT IN INCORRECT DOSING". The reverse mistake has been published as a case report of a man drawing U-100 insulin with U-40 syringes.

Which insulin syringe size should I buy — 0.3 mL, 0.5 mL or 1 mL?

Pick the smallest barrel your dose fits in, because the marks are further apart on it. A 0.3 mL barrel is numbered to 30 units, a 0.5 mL to 50 and a 1 mL to 100; embecta supplies all three, "with availability in 1 mL, 0.5 mL, and 0.3 mL capacities, with 6 mm, 8 mm and 12.7 mm needles". The 0.3 mL is also the only one the manufacturer states is offered with a half-unit scale.

Can an insulin syringe measure half a unit?

Only the 0.3 mL barrel is documented as being manufactured with a half-unit scale, where one printed mark is 0.005 mL. Figures on this page are rounded to the quarter unit, which is the finest a barrel can be read to — but a quarter unit is an eye estimate between two printed lines, not a line of its own. If a quarter of a unit matters to your dose, the concentration is too high: reconstitute to a weaker one so the same dose lands on more marks.

Is a 1 mL insulin syringe the same as a 1 mL syringe?

They hold the same volume and are numbered completely differently. A 1 mL insulin barrel is numbered 0 to 100 in units; a 1 mL luer-lock barrel is numbered 0 to 1 in millilitres. "Draw 0.5" means 0.005 mL on one and 0.5 mL on the other, a hundredfold difference. Insulin syringes also carry a fixed, fine, short needle, which is why oil solutions and intramuscular injections are not given with them.

Sources

1. [1]embecta (formerly BD Diabetes Care) — Insulin Syringes with Ultra-Fine needle: barrel capacities, needle lengths and the ½ unit scale on the 0.3 mL barrel
2. [2]FDA-approved label — VETSULIN (porcine insulin zinc suspension), Merck Animal Health, NADA 141-236 (DailyMed SPL): U-40 concentration and the U-40 syringe warning
3. [3]FDA Global Unique Device Identification Database — "EXEL U-40 1mL INS SYR 29GX1/2", Exel International, DI 00020221260373 (in commercial distribution)
4. [4]FDA Global Unique Device Identification Database — “Easy Glide INSULIN SYRIN 0.3 ML 30GX1/2” 1/2 UNIT MARKING”, DI B2086345030
5. [5]Nasr N, et al. Poorly Controlled Type 3c Diabetes due to Use of Veterinarian Insulin Syringes. Case Rep Endocrinol. 2019 (PMC6601479)