How much does 1 unit of insulin lower blood glucose levels?

How Much Does 1 Unit of Insulin Lower Blood Glucose Levels?

One unit of insulin typically lowers blood glucose by approximately 50 mg/dL (2.8 mmol/L), though this effect is highly individualized and varies based on patient-specific factors. 1

Insulin Sensitivity Factor (ISF)

The blood glucose-lowering effect of insulin is measured through the insulin sensitivity factor (ISF), which is defined as:

• The individualized measure of how much blood glucose will decrease with 1 unit of insulin 1
• For example, with an ISF ratio of 1:3,1 unit of insulin would lower blood glucose by 3 mmol/L (approximately 54 mg/dL) 1
• This factor varies significantly between individuals and must be determined for each patient 1

Factors Affecting Insulin's Glucose-Lowering Effect

Several factors influence how much 1 unit of insulin will lower blood glucose:

• Total daily insulin requirements: Typically ranges from 0.4 to 1.0 units/kg/day in adults with type 1 diabetes who are metabolically stable 1
• Patient weight: Heavier patients generally require more insulin and may have a smaller per-unit effect 1
• Insulin sensitivity: Varies based on individual metabolic factors 1
• Time of day: Many people require more insulin per carbohydrate in the mornings due to higher counter-regulatory hormone levels 1
• Physiological state: Higher insulin amounts may be required during puberty, menses, and medical illness 1

Clinical Application of ISF

When managing diabetes with insulin therapy:

• ISF is calculated from the total daily dose of insulin and reflects the patient's sensitivity to insulin 1
• This factor is programmed into insulin pumps for automated bolus calculations 1
• For correction boluses, the formula is: Correction dose = (Current glucose - Target glucose) ÷ ISF 1

Special Considerations

• Insulin stacking: Multiple frequent insulin doses can lead to overlapping effects and hypoglycemia 1
• Insulin timing: The glucose-lowering effect has different onset, peak, and duration depending on the insulin type 1
• Continuous insulin infusion: In hospital settings, IV insulin typically decreases plasma glucose at a rate of 50-75 mg/dL per hour at a dose of 0.1 unit/kg/hour 1

Common Pitfalls

• Assuming a fixed insulin effect: The same dose may have different effects in different patients or even in the same patient under different conditions 1
• Ignoring insulin on board: Modern insulin pumps track active insulin to prevent overdosing 1
• Overlooking diurnal variations: Insulin sensitivity often varies throughout the day 1
• Failing to adjust for changing requirements: ISF should be reassessed regularly as patient factors change 1

Remember that while 50 mg/dL per unit is a reasonable starting point for many adults, the actual glucose-lowering effect must be determined individually and may require adjustment over time based on observed responses to insulin therapy.