Somogyi Effect and Dawn Phenomenon

Medically Reviewed by Michael Dansinger, MD on August 25, 2022

For people who have diabetes, the Somogyi effect and the dawn phenomenon both cause higher blood sugar levels in the morning. The dawn phenomenon happens naturally, but the Somogyi effect usually happens because of problems with your diabetes management routine.

Insulin, Blood Sugar, and Sleep

Your body uses a form of sugar called glucose as its main source of energy. A hormone called insulin, which your pancreas makes, helps your body move glucose from your bloodstream to your cells.

While you sleep, your body doesn’t need as much energy. But when you’re about to wake up, it gets ready to burn more fuel. It tells your liver to start releasing more glucose into your blood. That should trigger your body to release more insulin to handle more blood sugar.

If you have diabetes, your body doesn’t make enough insulin to do that. That leaves too much sugar in your blood, a problem called hyperglycemia.

High blood sugar can cause serious health problems, so if you have diabetes, you’ll need help to bring those levels down. Diet and exercise help, and so can medications like insulin.

The Dawn Phenomenon

If you have diabetes, your body doesn’t release more insulin to match the early-morning rise in blood sugar. It’s called the dawn phenomenon, since it usually happens between 3 a.m. and 8 a.m.

The dawn phenomenon happens to nearly everyone with diabetes. But there are a few ways to prevent it, including:

  • Don’t eat carbohydrates before you go to bed.
  • Take insulin before bedtime instead of earlier in the evening.
  • Ask your doctor about adjusting your dose of insulin or other diabetes medicines.
  • Use an insulin pump overnight.

The Somogyi Effect

The Somogyi effect also causes high levels of blood sugar in the early morning. But it usually happens when you take too much or too little insulin before bed, or when you skip your nighttime snack.

When that happens, your blood sugar can drop sharply overnight. Your body responds by releasing hormones that work against insulin. That means you’ll have too much blood sugar in the morning. It’s also called rebound hyperglycemia.

How Do You Know Which One You Have?

Your doctor will want to find out why you’re waking up with high blood sugar before they tell you how to treat it. This means they’ll ask you to test your blood sugar in the middle of the night -- around 2 or 3 a.m. -- for several nights.

If your levels are always low during that time, it’s probably the Somogyi effect. If not, it’s likely the dawn phenomenon. Knowing which is which will help your doctor come up with a plan to address it.

Show Sources


The Cleveland Clinic: "What Causes High Blood Sugar in the Morning.”

National Institute of Diabetes and Digestive and Kidney Diseases: “What is diabetes?”

American Diabetes Association: “What Causes Hyperglycemia?” “Dawn phenomenon.”

Diabetes Care: “Nocturnal Blood Glucose Control in Type I Diabetes Mellitus.”

The Mayo Clinic: “The dawn phenomenon: What can you do?”

Diabetes Quebec: “The Somogyi effect or rebound hyperglycemia.”

© 2022 WebMD, LLC. All rights reserved. View privacy policy and trust info