What is the onset of action for subcutaneous (Sub Q) insulin lispro (Humalog)?

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Last updated: May 20, 2025View editorial policy

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From the Guidelines

Subcutaneous lispro insulin begins working within 5 minutes after injection. This rapid-acting insulin reaches its peak effect in about 1 to 2 hours and continues working for approximately 3 to 4 hours total, as shown in the study by 1. The quick onset makes lispro ideal for mealtime insulin coverage, as it can be administered just before eating.

Key Characteristics of Lispro Insulin

  • Onset of action: 5 minutes
  • Peak action: 1 to 2 hours
  • Duration of action: 3 to 4 hours For optimal blood glucose control, patients should time their injections accordingly—ideally just before starting a meal. Individual response times may vary based on factors such as injection site, blood flow to the area, temperature, physical activity, and individual metabolism. Patients should monitor their blood glucose levels after injection to understand their personal response pattern. Unlike regular human insulin, lispro's modified amino acid sequence allows for faster absorption into the bloodstream, making it more effective at mimicking the body's natural insulin response to meals, as described in the study by 1.

From the FDA Drug Label

When given subcutaneously, HUMALOG has a more rapid onset of action and a shorter duration of action than regular human insulin. HUMALOG should be given within 15 minutes before a meal or immediately after a meal.

The onset of action for subcutaneous lispro is rapid, but the exact time is not specified in the label. However, it is recommended to administer HUMALOG within 15 minutes before a meal or immediately after a meal, suggesting that it starts working quickly after injection 2.

From the Research

Time to Start Working

  • Sub Q lispro begins to exert its effects within 15 minutes of subcutaneous administration 3

Peak Levels

  • Peak levels of sub Q lispro occur 30 to 90 minutes after administration 3

Duration of Activity

  • The duration of activity of sub Q lispro is less than five hours 3

Comparison to Regular Human Insulin

  • Sub Q lispro has a faster absorption rate and a shorter duration of action compared to regular human insulin 4
  • Sub Q lispro reduces the postprandial rise in serum glucose and the rate of hypoglycemia compared to regular human insulin 4, 5

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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