Is Tresiba Fast-Acting?
No, Tresiba (insulin degludec) is not a fast-acting insulin—it is an ultra-long-acting basal insulin with a duration of action exceeding 42 hours. 1, 2
Classification and Pharmacokinetics
Tresiba is explicitly classified as a long-acting basal insulin analog used to cover the body's basal metabolic insulin requirement by regulating hepatic glucose production, not for controlling post-meal glucose excursions. 3, 1
The American Diabetes Association guidelines clearly distinguish degludec as a longer-acting basal analog alongside glargine U-300, separate from rapid-acting insulin analogs (aspart, glulisine, lispro) which are used for mealtime coverage. 3
Insulin degludec has an ultra-long duration of action of more than 42 hours with a half-life of 17-21 hours, roughly double that of insulin glargine. 2, 4
After subcutaneous injection, degludec forms a depot of soluble multihexamer chains with continuous slow dissociation of insulin monomers, reaching peak levels at 10-12 hours followed by a slow decline. 4, 5
Clinical Use and Dosing
Degludec is administered once daily (with flexible timing possible due to its ultra-long action) to provide 24-hour basal insulin coverage, not before meals. 3, 6
For type 1 diabetes, degludec must be combined with prandial (mealtime) rapid-acting insulin to control post-meal glucose excursions—basal insulin alone is insufficient. 2
For type 2 diabetes, degludec can be used alone or combined with oral antidiabetic agents, GLP-1 receptor agonists, or short-acting insulin depending on glycemic control needs. 2
Comparison to Actual Fast-Acting Insulins
Rapid-acting insulin analogs (aspart, glulisine, lispro) have a quick onset, peak within 1-2 hours, and short duration of action—these are the true fast-acting insulins used at mealtimes. 3
The pharmacokinetic profile of degludec is the opposite of fast-acting insulins: it has a flat, peakless profile with extended duration rather than rapid onset and short action. 7, 5
Common Pitfall to Avoid
- Do not confuse the combination product Ryzodeg (insulin degludec/insulin aspart) with Tresiba alone—Ryzodeg contains 70% degludec (long-acting) plus 30% aspart (rapid-acting), but Tresiba itself contains only the long-acting degludec component. 7