Insulin Unit to Milliliter Conversion
For standard U-100 insulin (100 units per mL), 1 unit of insulin equals 0.01 mL. 1, 2
Understanding Insulin Concentrations
The conversion between insulin units and milliliters depends entirely on the insulin concentration being used:
Standard U-100 Insulin (Most Common)
- U-100 insulin contains 100 units per 1 mL 1, 2, 3
- Therefore, 1 unit = 0.01 mL (or 1 mL = 100 units) 1, 2
- Standard insulin pens contain 300 units total in 3 mL cartridges 1, 2
- This is the most widely used insulin concentration globally 4, 5
Concentrated Insulin Formulations
For patients requiring higher doses, concentrated formulations have different conversions:
- U-200 insulin: 1 unit = 0.005 mL (200 units per mL) 4, 1
- U-300 insulin: 1 unit = 0.0033 mL (300 units per mL) 4, 6
- U-500 insulin: 1 unit = 0.002 mL (500 units per mL) 4, 7
Critical Safety Considerations
Never use standard insulin syringes with concentrated insulin formulations - this is a common and dangerous pitfall that can lead to severe dosing errors and life-threatening hypoglycemia 4, 6
Proper Syringe Matching
- U-100 insulin requires U-100 marked syringes 5, 8
- U-500 insulin requires dedicated U-500 syringes to prevent 5-fold dosing errors 4
- Concentrated insulins (U-200, U-300) are only available in prefilled pens specifically to minimize dosing errors 4, 1
Device Accuracy
- Insulin pens and pumps demonstrate superior accuracy compared to syringes, especially at low doses (1-2 units) 8
- Syringes can be dangerously inaccurate at 1-unit doses, with errors exceeding 100% when mixing insulins in dead-space-containing syringes 8, 9
- Modern low dead-space syringes are essential when mixing insulins to ensure dose accuracy 9
Practical Application
When prescribing or administering insulin, always verify: