How many units is 1 mg on an insulin syringe?
One milligram is the easiest dose to convert. A U-100 syringe holds 100 units per mL,[1] so for 1 mg the number of units is simply 100 divided by the strength in mg/mL. At 10 mg/mL that is 10 units (0.1 mL); at 5 mg/mL it is 20 units.
1 mg to units insulin syringe chart
| Strength | mL | Units (U-100) | Smallest syringe | Reading | One-unit misread |
|---|---|---|---|---|---|
| 1 mg/mL | 1 | 100 | 1 mL | On a line of the 1 mL syringe | ±1% |
| 2 mg/mL | 0.5 | 50 | 0.5 mL | On a line of the 0.5 mL syringe | ±2% |
| 2.5 mg/mL | 0.4 | 40 | 0.5 mL | On a line of the 0.5 mL syringe | ±2.5% |
| 3 mg/mL | 0.333 | 33.33 | 0.5 mL | Between the 33 and 34 lines (1-unit marks) | ±3% |
| 4 mg/mL | 0.25 | 25 | 0.3 mL | On a line of the 0.3 mL syringe | ±4% |
| 5 mg/mL | 0.2 | 20 | 0.3 mL | On a line of the 0.3 mL syringe | ±5% |
| 10 mg/mL | 0.1 | 10 | 0.3 mL | On a line of the 0.3 mL syringe | ±10% |
| 20 mg/mL | 0.05 | 5 | 0.3 mL | On a line of the 0.3 mL syringe | ±20% |
Strengths that divide 100 evenly, such as 2, 2.5, 4, 5, 10 and 20 mg/mL, give whole-unit answers. 3 mg/mL does not, and its row is flagged.
Two shortcuts worth knowing
units = 1 mg ÷ strength (mg/mL) × 100 = 100 ÷ strength
So at 4 mg/mL, 1 mg is 25 units, and at 20 mg/mL it is 5 units. The second shortcut: at 1 mg/mL, milligrams times 100 give units directly, which is why 1 mg is 100 units only at that one strength.
Some strengths do not divide evenly. At 3 mg/mL the answer is 33.33 units, which lands between two lines whatever the scale of a syringe that holds it.[2] Ask a pharmacist how to measure a dose like that. Do not guess.
1 mg is not 1 mL and not 1 unit
Milligrams measure the amount of drug. Millilitres measure volume. Units on a U-100 syringe are volume marks of 0.01 mL each. The three only line up at 1 mg/mL, where 1 mg is 1 mL, which is 100 units, the whole of a 1 mL syringe.[3] For the volume alone, see mg to mL.
Half this dose is charted in 0.5 mg to units and two and a half times it in 2.5 mg to units.
Frequently asked questions
How many units is 1 mg on an insulin syringe?
100 divided by the strength in mg/mL. At 10 mg/mL it is 10 units; at 2 mg/mL it is 50 units.
How many mcg is 1 mg?
1,000 mcg.
Can 1 mg be measured on a 0.3 mL syringe?
Yes, when it comes to 30 units or less: a strength above about 3.3 mg/mL. In the table that is 4 mg/mL and stronger.