Maximum Effect of Lispro Insulin
Lispro insulin reaches its maximum effect (peak action) 1-2 hours after subcutaneous injection. 1, 2, 3
Pharmacodynamic Profile
The time course of lispro insulin's glucose-lowering activity follows a predictable pattern:
- Onset of action: 5-15 minutes after subcutaneous administration 2, 3
- Peak effect: 30-90 minutes after injection, with most studies showing peak activity at 1-2 hours 1, 2, 3
- Duration of action: 3-5 hours total 1, 2, 3
Clinical Implications
This rapid peak effect distinguishes lispro from regular human insulin, which peaks 50-120 minutes after injection and has a longer duration of action. 1 The earlier and more pronounced peak of lispro makes it ideal for controlling postprandial glucose excursions when administered immediately before meals (within 15 minutes). 4, 2
Optimal Timing for Administration
Lispro should be injected 15 minutes or less before meals to align its peak effect with postprandial glucose rise. 4, 2 In hyperglycemic patients (glucose >10 mmol/L or ~180 mg/dL), administering lispro 15-30 minutes before the meal further improves postprandial glucose control compared to injection at mealtime. 5
Practical Considerations
The concentrated peak at 1-2 hours means:
- Maximum glucose-lowering occurs during the early postprandial period 1, 2
- Risk of hypoglycemia is highest 1-2 hours after injection 3
- The effect wanes significantly by 3-4 hours, requiring adequate basal insulin coverage to prevent late postprandial hyperglycemia 6
Common pitfall: Patients must understand lispro's rapid onset and peak to avoid hypoglycemia if meals are delayed after injection. 4 The short duration also means lispro should never be used at bedtime due to increased nocturnal hypoglycemia risk. 7