Standard International Unit for Insulin Dosing
The standard international unit (IU) is the universally accepted unit for insulin dosing, with insulin typically available in concentrations of 100 units per mL (U-100) as the most common formulation. 1, 2
Understanding Insulin Units
Insulin dosing uses a bioefficacy-based unit system rather than mass-based measurements:
- Standard concentration: 100 units/mL (U-100) is the most common formulation
- More concentrated formulations are also available:
Clinical Significance of IU
The international unit system provides several advantages:
- Standardization across different insulin types and manufacturers
- Precise dosing calculations for patient safety
- Consistent documentation in medical records
- Compatibility with insulin delivery devices calibrated in IU
Insulin Dosing Guidelines
Insulin dosing follows established protocols based on patient needs:
Initial Dosing
- For basal insulin: Start with 10 units/day or 0.1-0.2 units/kg/day 1
- For Type 1 diabetes: Typically 0.5 units/kg/day total, with 50% as basal and 50% as prandial insulin 1
- For Type 2 diabetes: Dosing depends on degree of insulin resistance and hyperglycemia 1
Dose Adjustments
- Evidence-based titration: Increase by 2 units every 3 days until fasting plasma glucose goals are reached 1
- For hypoglycemia: Reduce dose by 10-20% if no clear cause is identified 1
Practical Applications of Insulin Units
Prandial Insulin Calculation
The formula for calculating rapid-acting insulin doses uses IU:
- Dose (IU) = (Carbohydrates ÷ carbohydrate ratio) + (current glucose - target glucose) ÷ insulin sensitivity factor 2
Carbohydrate Coverage
- Typically 1 IU covers 10-15g of carbohydrates in enteral nutrition 2
- Insulin sensitivity factor can be estimated by dividing 1800 by the total daily dose of insulin 2
Common Pitfalls in Insulin Unit Usage
- Confusion between different concentrations: Ensure the correct insulin concentration is used when calculating doses
- Conversion errors: When converting between IU/mL and SI units (pmol/L), use the correct conversion factor to avoid underreporting insulin concentrations by ~15% 5
- Dosing irregularities: Missed, mistimed, or reduced doses are common and can impact glycemic control 6
- Device-specific considerations: Different insulin delivery devices may have different markings and increments
Special Considerations
- For patients requiring large insulin doses, concentrated insulins (U-200, U-300, U-500) allow delivery of higher doses with smaller injection volumes 3, 4
- Some concentrated insulins (insulin degludec U-200, insulin lispro U-200) are bioequivalent to their U-100 counterparts, while others (regular human insulin U-500, insulin glargine U-300) have different pharmacokinetic properties 4
The international unit (IU) system provides a standardized approach to insulin dosing that enhances patient safety and treatment efficacy across different insulin formulations and delivery methods.