How the Somogyi Effect Causes High Morning Blood Sugar

Woman injecting herself with insulin
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The Somogyi effect is one type of morning high blood sugar (hyperglycemia) caused by very low blood sugar (hypoglycemia) during the night. It is also called the rebound effect or rebound hyperglycemia. It's a very rare phenomenon and most often occurs in people with type 1 diabetes.

How the Somogyi Effect Works

Your body tries to keep your blood sugar levels stable.

When blood glucose levels drop during sleep, your body releases hormones that trigger the liver to release glucose. This influx of glucose into the bloodstream can then raise your blood sugar levels beyond what's normal for fasting glucose levels, leading to a high-fasting glucose reading the next morning.


The Somogyi effect results from having extra insulin your body before bedtime. Insulin is a hormone produced by the beta cells of the pancreas that permits glucose to enter cells and helps the body use glucose for energy. Insulin controls the amount of glucose in the blood.

There are a couple ways you could have too much insulin at bedtime:

  1. Not having a bedtime snack (which would give the insulin some glucose to work on)
  2. Taking long-acting insulins. Because it's often an effect of long-acting insulins, the Somogyi effect mainly occurs in people with type 1 diabetes.

How the Somogyi Effect Differs from the Dawn Phenomenon

The Somogyi effect is similar to the dawn phenomenon in that both can cause high morning blood glucose readings as a result of a hormone triggering the liver to release glucose into the blood.

Unlike the Somogyi effect, however, the dawn phenomenon is not caused by hypoglycemia, but by a random release of the triggering hormones.

The only way to know for sure whether you're experiencing the dawn phenomenon or the Somogyi effect is to test your blood sugar in the middle of the night.

Wake up sometime between 2 and 3 a.m. for several nights in a row, and check your blood sugar.

If you are low at that time, it could be the Somogyi effect. If you are normal or high, then the dawn phenomenon may be the culprit.

How to Counteract It

To counteract high morning blood sugars, there are two major steps you can take:

  • Make sure to have a snack before bed that consists of more protein than carbs. For instance, you could have some nuts or cheese.
  • Let your doctor know what is happening. He or she may change your medication or insulin dosages, or change the timing of when you should receive insulin.


The Somogyi effect is named for Michael Somogyi, Ph.D., a Hungarian biochemist in the 1930s who is credited with discovering the chain of events that results in rebound morning hyperglycemia.