Insulin Units to mL Calculator
Convert between insulin units and millilitres for any concentration: U-40, U-100, U-200, U-300, U-500. Critical for correct syringe selection. Educational use only.
🔬 Units ↔ mL Converter
Conversion Result
How to Use This Calculator
- Select your insulin concentration — U-100 is standard; U-40 is mostly veterinary.
- Choose the direction — units → mL, or mL → units.
- Enter the amount and convert. The result shows the volume (or units) with the calculation and a quick-reference table.
Use the volume only with a syringe that matches the concentration. For U-200, U-300 and U-500, dose with the dedicated pen rather than drawing a volume.
Insulin Concentration Explained
The Formula
Example (U-100): 20 units ÷ 100 = 0.2 mL. Example (U-40): 20 units ÷ 40 = 0.5 mL. The same unit dose occupies more volume in a less concentrated insulin.
Common Insulin Concentrations
| Concentration | Units/mL | Common Products | Syringe Required |
|---|---|---|---|
| U-40 | 40 | Vetsulin, Caninsulin (pets) | U-40 syringe |
| U-100 | 100 | Lantus, Levemir, Humalog, NovoLog, Humulin N/R, Novolin N/R | U-100 syringe (standard) |
| U-200 | 200 | Humalog U-200 KwikPen | Pre-measured pen — no syringe drawing |
| U-300 | 300 | Toujeo (glargine 300) | Pre-measured pen — no syringe drawing |
| U-500 | 500 | Humulin R U-500 (severe resistance) | U-500 syringe or dedicated pen |
U-200, U-300, and U-500 insulins are typically dispensed in dedicated pens that dose in units — not drawn up in syringes. Never draw U-300 or U-500 into a standard U-100 syringe. If you must draw from a U-500 vial, use a U-500 syringe or consult your pharmacist for specific instructions.
Reading the Volume on an Insulin Syringe
Syringe sizes and markings
Standard U-100 insulin syringes come in three capacities, and the right one makes small doses easier to read accurately:
| Syringe size | Holds up to | Best for |
|---|---|---|
| 0.3 mL (3/10 cc) | 30 units | Small doses; often has half-unit marks |
| 0.5 mL (1/2 cc) | 50 units | Mid-range doses |
| 1 mL (1 cc) | 100 units | Larger doses (lines often = 2 units) |
Drawing the dose without errors
On a U-100 syringe each numbered line is units, not millilitres, so 30 units is simply the "30" mark — no volume math needed. Draw a little air into the syringe first, inject it into the vial to ease withdrawal, then pull to the unit mark and tap out air bubbles, which otherwise reduce the real dose. Keep the syringe and the insulin at the same concentration.
Sources & References
- FDA. Insulin products labeling. Various manufacturers.
- American Diabetes Association. Standards of Medical Care — 2024. Section 9.
- Institute for Safe Medication Practices (ISMP). Insulin Safety. Link
Last reviewed: June 2025
Frequently Asked Questions
How many units are in 1 mL of insulin?
It depends on the concentration. U-100 (the most common human insulin): 100 units/mL. U-40 (e.g., Vetsulin for pets): 40 units/mL. U-200 (Humalog U-200): 200 units/mL. U-300 (Toujeo): 300 units/mL. U-500 (Humulin R U-500): 500 units/mL. Always check the label and use the syringe that matches your concentration.
How do I convert insulin units to mL?
Divide units by concentration: mL = Units ÷ Concentration. For U-100: 20 units ÷ 100 = 0.2 mL. For U-40: 20 units ÷ 40 = 0.5 mL. To convert back: Units = mL × Concentration. Always match the syringe markings to the concentration being used.
What happens if I use a U-100 syringe with U-40 insulin?
Using a U-100 syringe with U-40 insulin causes a 2.5× underdose — you draw what appears to be 25 units on the syringe, but actually contains only 10 units of U-40. Conversely, using a U-40 syringe with U-100 insulin causes a 2.5× overdose — 10 units marked on a U-40 syringe delivers 25 units of U-100. Both errors can be clinically dangerous. This is especially critical for pet owners using Vetsulin (U-40).
What is the most common insulin concentration?
U-100 is the global standard for human insulin — essentially all insulins dispensed in the US, Canada, UK, and Australia for human use are U-100, unless the label specifically states otherwise. Standard insulin syringes sold in pharmacies are U-100. U-40 is used for some veterinary insulins. U-200, U-300, and U-500 are available for specific populations (high-dose, insulin-resistant patients) but are always dispensed with dedicated pens or specific instructions.
How many mL is 50 units of insulin?
For standard U-100 insulin, 50 units is 0.5 mL (50 ÷ 100). At U-40 the same 50 units would be 1.25 mL, and at U-200 it would be 0.25 mL. On a U-100 syringe you simply draw to the "50" mark — no volume conversion needed.
What size insulin syringe do I need?
Match the syringe to your largest usual dose: a 0.3 mL syringe holds up to 30 units (and often has half-unit marks for fine dosing), a 0.5 mL holds up to 50 units, and a 1 mL holds up to 100 units. Smaller syringes make small doses easier to read accurately. All are U-100 — use them only with U-100 insulin.