Onset of Action of Insulin Glargine
Insulin glargine begins to lower blood sugar approximately 1 hour after subcutaneous injection. 1, 2
Pharmacokinetic Profile
Insulin glargine has an onset of action of approximately 1 hour after subcutaneous injection, with a duration of action of approximately 24 hours, allowing for once-daily dosing. 1
Key Timing Characteristics
- Onset: Approximately 1 hour after injection 1, 2
- Peak: No pronounced peak—provides a relatively constant concentration profile over 24 hours 1, 3
- Duration: Approximately 24 hours 1, 2
The FDA label confirms that after subcutaneous injection, insulin serum concentrations indicate a slower, more prolonged absorption with a relatively constant concentration/time profile over 24 hours with no pronounced peak compared to NPH insulin 2.
Clinical Implications of the Peakless Profile
The absence of a pronounced peak action time distinguishes insulin glargine from intermediate-acting insulins like NPH and makes it an ideal basal insulin 1. This peakless profile provides several clinical advantages:
- Reduced hypoglycemia risk: The lack of peak action reduces the risk of hypoglycemia, especially nocturnal hypoglycemia, compared to NPH insulin 1, 4, 5
- Stable glucose levels: Allows for more stable blood glucose levels between meals and overnight 1
- Physiologic basal insulin: Slowly releases insulin over 24 hours, causing more physiologic basal insulin levels 1
Duration of Pharmacological Effect
The median time between subcutaneous injection and the end of pharmacological effect is 24 hours (range: 10.8 to >24 hours) for insulin glargine, compared to 14.5 hours (range: 9.5 to 19.3 hours) for NPH insulin 2. This extended duration allows for true once-daily dosing in most patients.
Administration Timing Flexibility
While insulin glargine is typically administered once daily at bedtime, it can be given at any time of day with similar efficacy 1. However, blood glucose levels may rise around the time of injection regardless of when it is given during the day 6. The American Diabetes Association notes that timing can be adjusted based on individual patient needs and convenience 1.