How many units are in a 10 mL vial of U-40 insulin?
A 10 mL vial of U-40 insulin holds 400 units (10 mL × 40 units per mL); a 10 mL vial of U-100 insulin holds 1,000 units. Injections per vial = total units ÷ units per injection, so at 5 units per injection a 10 mL U-40 vial holds 80 injections, or 40 days at two injections a day. Each 5-unit draw on a U-40 syringe is 0.125 mL.
Insulin units → mL and syringe mark (premixed insulin, no mixing step)
= 0.125 mL of U-40 insulin
Volume = 5 units ÷ 40 units/mL = 0.125 mL Mark = 0.125 mL × 40 = 5 on a U-40 syringe
U-40 syringe · 40-unit barrel. Illustration only; read the marks on your actual syringe.
Math only, not medical advice. Confirm with your veterinarian.
The math
Total units = vial mL × U-number U-40: 10 mL × 40 = 400 units U-100: 10 mL × 100 = 1,000 units Injections per vial = total units ÷ units per injection Example: 400 ÷ 5 = 80 injections; 80 ÷ 2 per day = 40 days Volume per injection = units ÷ 40 = 5 ÷ 40 = 0.125 mL
| Units per injection | mL per injection (U-40) | Injections per 10 mL U-40 vial | Days at 2 per day |
|---|---|---|---|
| 1 | 0.025 | 400 | 200 |
| 2 | 0.05 | 200 | 100 |
| 3 | 0.075 | 133 | 66 |
| 4 | 0.1 | 100 | 50 |
| 5 | 0.125 | 80 | 40 |
| 6 | 0.15 | 66 | 33 |
| 8 | 0.2 | 50 | 25 |
| 10 | 0.25 | 40 | 20 |
| 12 | 0.3 | 33 | 16 |
| 15 | 0.375 | 26 | 13 |
| 20 | 0.5 | 20 | 10 |
Read the total off the label
The U-number is units per mL and the vial size is printed in mL, so total units = mL × U-number. A 10 mL U-40 vial is 400 units, a 10 mL U-100 vial is 1,000 units, and a 2.5 mL U-40 vial is 100 units. The same mL of U-100 insulin always holds 2.5× the units of U-40 insulin.
Worked examples
10 mL U-40 vial at 4 units per injection: 400 ÷ 4 = 100 injections, or 50 days at two a day. Each draw is 4 ÷ 40 = 0.1 mL.
10 mL U-40 vial at 10 units per injection: 400 ÷ 10 = 40 injections, or 20 days at two a day. Each draw is 0.25 mL.
10 mL U-100 vial at 8 units per injection: 1,000 ÷ 8 = 125 injections, or 62 full days at two a day. Each draw is 8 ÷ 100 = 0.08 mL.
Counts in the table are rounded down to whole injections.
Why the real count comes out a little lower
The math assumes every drop leaves the vial. In practice a small amount stays in the vial and the needle, and tapping out air bubbles can waste a little more, so treat the result as an upper limit. An opened vial also has a use-by period printed in its leaflet, which can end before the units run out; the label and your vet have that number, not this page.
Confirm with your veterinarian: These pages convert syringe marks and volumes only; the number of units your pet gets, and the syringe type to use, come from your vet.
Math only, not medical advice. This page converts numbers; it does not recommend any compound or amount.