In a rapid-acting insulin product, the insulin molecule has been modified to make it absorb as quickly as possible and better correspond with the normal insulin production of the pancreas in connection with a meal.
Rapid-acting insulin has an onset of action of 10–20 minutes, peak effect in 1–2 hours and duration of action of 2–5 hours, depending on the individual and the dose.
Rapid-acting insulin products include (10/2023) insulin aspart (brand names: Fiasp, Insulin Aspart Sanofi and NovoRapid), insulin glulisine (brand name: Apidra) and insulin lispro (brand names: Humalog, Insulin Lispro Sanofi, Liprolog). In the main, they work in a largely similar manner, i.e. in most cases, it does not really matter which rapid-acting insulin is used. That said, there may be individual differences in the effect of the products depending on the user.
Fiasp (faster acting insulin aspart) is slightly different compared to other rapid-acting insulins. Fiasp has an onset of action of approximately 5 minutes faster than other rapid-acting insulins. For some people, it works better than other rapid-acting insulins.