This Dawn phenomenon (Dawn phenomenon) describes the natural increase in blood sugar levels in the early morning hours between around 4 a.m. and 8 a.m. - without prior food intake. It occurs primarily in people with diabetes and leads to elevated fasting blood sugar levels in the morning.
Causes and pathophysiology
The phenomenon is triggered by hormonal changes at night. The following hormones increase in the early morning hours:
- Growth hormone (somatotropin)
- Cortisol
- Glucagon
- Adrenaline
These hormones promote the release of glucose from the liver while reducing the effects of insulin. This causes blood sugar to rise without eating anything.
Symptoms and effects
- Elevated fasting blood sugar in the morning (often 30-100 mg/dL higher than at night)
- Difficulty keeping blood sugar stable in the morning
- No drop in blood sugar at night
Differential diagnosis: Dawn phenomenon vs. Somogyi effect
| criterion | Dawn phenomenon | Somogyi effect |
|---|---|---|
| Cause | Hormonal surge in the morning | Counterregulation after nocturnal hypoglycemia |
| Blood sugar at 3am | normal or slightly increased | greatly degraded |
| blood sugar in the morning | increased | increased (rebound) |
Therapy and countermeasures
Treatment depends on the cause and usually includes:
- Adjustment of basal insulin (later injection or higher dose)
- With an insulin pump: increased basal rate in the morning hours
- Avoiding late-night, high-carbohydrate meals
- Regular exercise in the evening
- If necessary, medication to inhibit morning glucose production
Further information:
→ Diabetes mellitus – knowledge and overview
→ Why hyporest
→ Hyperglycemia
Sources
- German Diabetes Society (DDG). S3 guideline “Diabetes mellitus type 1 and type 2”. 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
