GLP-1 vial: convert mg to syringe units
Divide the amount in mg by the vial's concentration in mg/mL, then multiply by 100 for a U-100 syringe. Example: a 10 mg GLP-1 vial mixed with 2 mL of water is 5 mg/mL, so 0.5 mg is 0.1 mL, which is 10 units on a U-100 syringe. If the label already gives mg per mL, skip the first step and use that number.
Concentration = 10 mg ÷ 2 mL = 5 mg/mL Volume = 500 mcg ÷ 5000 mcg/mL = 0.1 mL Units = 0.1 mL × 100 (U-100) = 10 units
U-100 syringe · 100-unit barrel. Illustration only; read the marks on your actual syringe.
Math only, not medical advice. Verify every number yourself.
The math
Step 1: concentration (mg/mL) = vial mg ÷ water mL Step 2: volume (mL) = amount mg ÷ concentration Step 3: units = mL × 100 (U-100), × 50 (U-50), × 40 (U-40) Shortcut (U-100): units = amount mg × 100 ÷ concentration Example: 10 mg ÷ 2 mL = 5 mg/mL; 0.5 ÷ 5 = 0.1 mL = 10 units
| Example amount | U-100 units at 2.5 mg/mL | at 5 mg/mL | at 10 mg/mL |
|---|---|---|---|
| 0.1 mg | 4 | 2 | 1 |
| 0.25 mg | 10 | 5 | 2.5 |
| 0.5 mg | 20 | 10 | 5 |
| 1 mg | 40 | 20 | 10 |
| 1.5 mg | 60 | 30 | 15 |
| 2 mg | 80 | 40 | 20 |
Read the label first: total mg or mg per mL
A vial of powder lists the total amount in mg, and the concentration depends on how much water goes in: 10 mg in 2 mL is 5 mg/mL, 10 mg in 4 mL is 2.5 mg/mL. A vial that is already liquid usually prints its concentration, such as 5 mg/mL, or a total over a volume, such as 10 mg/2 mL, which is the same 5 mg/mL. Mixing up the total with the per-mL number is the most common way to be off by a large factor.
Worked examples
10 mg vial + 2 mL water (5 mg/mL): 1 mg ÷ 5 = 0.2 mL = 20 units on a U-100 syringe.
5 mg vial + 2 mL water (2.5 mg/mL): 0.25 mg ÷ 2.5 = 0.1 mL = 10 units.
Liquid labeled 10 mg/mL: 0.5 mg ÷ 10 = 0.05 mL = 5 units. The same 0.5 mg is 10 units at 5 mg/mL and 20 units at 2.5 mg/mL; the amount never changes, only the volume it takes up.
Small amounts and reading the barrel
Amounts in the table are arbitrary examples for the arithmetic, not suggested amounts. Results under about 5 units are hard to read on a 1 mL U-100 syringe, whose lines are usually 2 units apart. A 0.3 mL or 0.5 mL barrel spreads each unit over more length, and a 0.3 mL barrel often has half-unit lines. With a powder vial, more water gives a larger, easier-to-read draw for the same amount.
Common mistakes
mg vs mcg: 0.5 mg is 500 mcg, and entering one as the other is off by 1,000×. U-number: the unit math above is for U-100 syringes; on a U-40 barrel the same 0.1 mL is the 4 mark, not 10. Write the concentration on the vial so the math only has to be done once.
Note: The amount per injection comes from your prescriber or pharmacist; this page only converts an amount you already have into a syringe mark.
Math only, not medical advice. This page converts numbers; it does not recommend any compound or amount.