Is Insulin Glargine Long-Acting?
Yes, insulin glargine is definitively a long-acting insulin analog with a 24-hour duration of action and no pronounced peak, making it ideal for once-daily basal insulin coverage. 1, 2, 3
Pharmacokinetic Classification
Insulin glargine is officially classified as a long-acting insulin by the FDA, designed specifically to provide basal insulin coverage for glycemic control in adults and children with diabetes mellitus 1
The onset of action occurs approximately 1 hour after subcutaneous injection, with a duration of action of approximately 24 hours 2, 3
The defining characteristic is the absence of any pronounced peak action time, providing a relatively constant concentration profile over the full 24-hour period 2, 3, 4
Comparison to Other Insulin Types
The following pharmacokinetic profile distinguishes insulin glargine from other insulin categories:
Rapid-acting insulins (aspart, lispro): 5-minute onset, 1-2 hour peak, 3-4 hour duration 2
Short-acting insulin (regular): 15-minute onset, 3-4 hour peak, 6-8 hour duration 2
Intermediate-acting insulin (NPH): 1-hour onset, 6-8 hour peak, 12-hour duration 2
Long-acting insulin glargine: 1-hour onset, no peak, 24-hour duration 2, 3
Clinical Advantages of the Long-Acting Profile
The peakless, extended duration reduces hypoglycemia risk compared to intermediate-acting insulins like NPH, particularly nocturnal hypoglycemia 2, 3, 5
The flat pharmacokinetic profile allows for more stable blood glucose levels between meals and overnight, mimicking physiologic basal insulin secretion more closely than NPH insulin 3, 6
Once-daily dosing is sufficient due to the 24-hour duration, though it must be administered at the same time each day 1
Administration Considerations
Insulin glargine is typically dosed as basal insulin at 16-24 units once daily for patients with type 1 diabetes who do not use insulin pumps 2
It should not be mixed with other insulins due to the low pH of its diluent, which distinguishes it from intermediate-acting insulins that can be mixed 2
The medication slowly releases insulin over 24 hours from a subcutaneous depot, creating more physiologic basal insulin levels than pulsatile intermediate-acting formulations 2, 3