Insulin Conversion Calculator
Convert between insulin units, millilitres (mL), and different concentrations (U-40, U-100, U-200, U-300, U-500).
How to Use This Calculator
- Pick a conversion mode — units → mL, mL → units, or units from one concentration to another.
- Enter the dose or volume and select the insulin concentration (U-100 is standard).
- Read the result, with the working shown so you can check it.
This is an educational reference. For U-200, U-300 and U-500 insulin, dose with the matching prefilled pen (which counts in units) rather than drawing a volume by hand.
Concentration Reference
| Concentration | Units per mL | mL per 100 units | Common Use |
|---|---|---|---|
| U-40 | 40 | 2.5 mL | Veterinary; some international markets |
| U-100 | 100 | 1.0 mL | Standard worldwide (pens + vials) |
| U-200 | 200 | 0.5 mL | Tresiba U-200, Humalog U-200 pen |
| U-300 | 300 | 0.33 mL | Toujeo pen only |
| U-500 | 500 | 0.2 mL | Humulin R U-500 (special syringe required) |
Why Insulin Comes in Different Concentrations
U-100 — 100 units per millilitre — is the global standard, but higher concentrations exist so people who need large doses can inject a smaller, more comfortable volume. A 60-unit dose is 0.6 mL of U-100 but only 0.2 mL of U-300. Concentrated insulins (U-200, U-300, U-500) are sold almost exclusively in prefilled pens that count in units, so you never have to do the volume math yourself.
The danger appears when concentration and delivery device don't match. The number of units stays the same when you switch concentrations — a 50-unit dose is 50 units whether it is U-100 or U-200 — but the volume changes, which is why a U-100 syringe must never be used to draw a different concentration.
Switching Insulin Concentrations Safely
Units usually stay the same
When your prescriber moves you between concentrations, the starting dose is normally unit-for-unit — 30 units of U-100 basal becomes 30 units on the new pen. The pen counts in units, so you don't recalculate volumes yourself.
When the dose may change
Some concentrated insulins behave a little differently. Switching to glargine U-300 (Toujeo) sometimes needs a slightly higher dose to reach the same effect, and switching from Toujeo back to a U-100 basal is often reduced by about 20% to avoid lows. These adjustments are made by your care team from your glucose readings — never change concentration on your own.
Frequently Asked Questions
How do I convert between insulin concentrations?
Units stay the same across concentrations — a 40-unit dose is 40 units whether it is U-100 or U-200. Only the volume changes. Use this converter to find the volume, but for U-200/U-300/U-500 always dose with the matching prefilled pen, which counts in units.
Is U-100 the same dose as U-200?
The same number of units delivers the same dose. The difference is volume: 40 units of U-200 is half the volume (0.2 mL) of 40 units of U-100 (0.4 mL). Never draw U-200 into a U-100 syringe.
What is U-500 insulin?
U-500 is a highly concentrated insulin (500 units per mL) for people with severe insulin resistance who need very large doses. It requires a dedicated U-500 syringe or pen, never a standard syringe.
What happens if I use the wrong concentration syringe?
It causes a serious dosing error. Drawing U-100 insulin into a U-40 syringe gives 2.5 times the intended dose; the reverse under-doses. Always match the syringe — or the pen — to the insulin's concentration.
How many units are in 1 mL of insulin?
It depends on the concentration. 1 mL of U-100 is 100 units, U-40 is 40 units, U-200 is 200 units, U-300 is 300 units, and U-500 is 500 units. The "U" number is exactly the units per millilitre, which is why the volume changes but the unit dose does not.
Can I switch from U-100 to U-300 (Toujeo) unit for unit?
The usual starting point is unit-for-unit, but glargine U-300 (Toujeo) can need a slightly higher dose to match a U-100 basal, and switching back to U-100 is often reduced by about 20% to avoid lows. Your prescriber sets the exact conversion and adjusts it from your glucose readings.
Reference
- FDA. Insulin U-500 — Special Syringe Required. Drug Safety Communication, 2016.
- Insulin product labeling (U-40, U-100, U-200, U-300, U-500).
Last reviewed: June 2025