Fast-acting insulin (also Bolus insulin or Mealtime insulin called) is injected directly with meals in order to counteract the rise in blood sugar after eating or to specifically correct elevated values. It mimics as closely as possible the natural insulin rise after a meal and is a central component of intensified insulin therapy (ICT) and insulin pump therapy.
Mode of action
Rapid-acting insulin begins to work just 5-15 minutes after injection, reaches its maximum after 1-2 hours and is largely broken down after 3-5 hours. It promotes the absorption of glucose from the blood into cells and inhibits glucose production in the liver.
Important active ingredients and preparations (as of 2026)
| active ingredient | Brand names | Start of effect | Effective maximum | Duration of action |
|---|---|---|---|---|
| Insulin aspart | NovoRapid, Fiasp (Ultra-rapid) | 5-15 mins | 1-2 hours | 3-5 hours |
| Insulin lispro | Humalog, Lyumjev (Ultra-rapid) | 5-15 mins | 1-2 hours | 3-5 hours |
| Insulin glulisine | Apidra | 10-20 mins | 1-2 hours | 3-5 hours |
Advantages
- Good control of mealtime blood glucose
- Can be used flexibly (ultra-rapid variants such as Fiasp and Lyumjev allow injections directly after eating)
- Lower risk of late hypoglycemia compared to older regular insulin
Disadvantages and risks
- High risk of hypoglycemia if the dosage is incorrect or a meal is forgotten
- Weight gain possible
- Several injections per day necessary (with ICT or pump)
Further information:
→ Diabetes mellitus – knowledge and overview
→ Why hyporest
→ Type 2 diabetes
Sources
- German Diabetes Society (DDG). S3 guideline “Type 2 diabetes”. As of 2025. Available at: www.deutsche-diabetes-gesellschaft.de/leitlinien.
- American Diabetes Association. Standards of Medical Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). Available at: diabetesjournals.org.
- Robert Koch Institute (RKI). Federal health reporting – diabetes mellitus in Germany. Berlin 2024.
- International Diabetes Federation (IDF). IDF Diabetes Atlas. 11th edition. Brussels 2025. Available at: diabetesatlas.org.
Important note:
The information in this encyclopedia article is intended solely for general and non-binding information. They do not replace medical advice, diagnosis or therapy. If you have any health questions or complaints, please always consult a doctor or qualified healthcare professional. The content was created with the greatest possible care, but errors cannot be completely ruled out.
Last updated: February 26, 2026
