The dawn phenomenon and the Somogyi effect cause high blood sugar levels, especially in the morning before breakfast, in people who have diabetes.
The dawn phenomenon is a normal rise in blood sugar as a person's body prepares to wake up.
- In the early morning hours, hormones (growth hormone, cortisol, and catecholamines) cause the liver to release large amounts of sugar into the bloodstream. For most people, the body produces insulin to control the rise in blood sugar.
- If the body doesn't produce enough insulin, blood sugar levels can rise. This may cause high blood sugar in the morning (before eating).
If the blood sugar level drops too low in the early morning hours, hormones (such as growth hormone, cortisol, and catecholamines) are released. These help reverse the low blood sugar level but may lead to blood sugar levels that are higher than normal in the morning. An example of the Somogyi effect is:
- A person who takes insulin doesn't eat a regular bedtime snack, and the person's blood sugar level drops during the night.
- The person's body responds to the low blood sugar by releasing hormones that raise the blood sugar level. This may cause a high blood sugar level in the early morning.
How can you tell the difference?
The Somogyi effect can occur any time you or your child has extra insulin in the body. To sort out whether an early morning high blood sugar level is caused by the dawn phenomenon or Somogyi effect, check blood sugar levels at bedtime, around 2 a.m. to 3 a.m., and at your normal wake-up time for several nights. A continuous glucose monitor could also be used throughout the night.
- If the blood sugar level is low at 2 a.m. to 3 a.m., suspect the Somogyi effect.
- If the blood sugar level is normal or high at 2 a.m. to 3 a.m., it's likely the dawn phenomenon.
Current as of: December 20, 2019
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Donald Sproule, MDCM, CCFP - Family Medicine
Adam Husney, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator