The Types of Insulin, Explained
Reviewed by CDE Mehandi Sharma · Updated
Insulin is not one drug. The different types are the same hormone packaged to act over different timeframes, and a Type 1 regimen combines them.
| Type | Starts working | Peaks | Lasts |
|---|---|---|---|
| Rapid-acting | About 15 minutes | About 1 to 2 hours | About 2 to 4 hours |
| Rapid-acting inhaled | About 10 to 15 minutes | About 30 minutes | About 1.5 to 3 hours |
| Short-acting | About 30 to 60 minutes | About 2 to 3 hours | About 3 to 6 hours |
| Intermediate-acting | About 2 to 4 hours | About 4 to 12 hours | About 12 to 18 hours |
| Long-acting | About 1.5 to 4 hours | No real peak | About 24 hours |
| Ultra long-acting | About 6 hours | No real peak | 36 hours or more |
Reading the table tells you what each one is for. The rapid and short-acting types are taken around meals, to cover the glucose from food. The long-acting types have no peak, which is exactly what you want for background cover through the day and night.
Premixed insulins combine two types in one pen. They mean fewer injections and less flexibility, which is a genuine trade rather than a compromise.
Knowing your own insulin's peak and duration is practical, not academic. It tells you how long a correction dose is still working, which is what stops you stacking doses on top of each other.