Onset is the length of time before insulin reaches the bloodstream and begins lowering blood glucose. Insulins with long onset (2 to 4 hours) are typically the long-acting insulins, or those that have long duration. Those insulins with the shortest onset times (30 minutes) belong to the fast-acting category, or those with relatively short duration. The intermediate-acting insulins have a 1-2 hour onset with 8-12 hours of duration.
Working with Onset
A predictable, slow onset is a necessary part of working with overlap. Insulins with short onset frequently peak in less than 4 hours after injection. Food can be given to extend onset and peak response.