High Morning Blood Sugar: Dawn Phenomenon versus Somogyi Effect

Conditions that Can Make Your Morning Glucose Levels High

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If you've tested your blood glucose before breakfast and thought "wow, that's higher than usual," there are a few things that could be going on. Find out what can cause high morning blood sugar and what to do about it.

Five Tips for Easy Blood Sugar Monitoring

The Most Likely Culprit

The most likely cause of high morning glucose is not taking an adequate dose of insulin at night. Counter-regulatory hormones can rise in the early morning and make morning glucose tougher to treat.

If this is the problem, you may need either higher nighttime doses or take your insulin dose closer to bedtime.

Somogyi Effect

Less often the problem may be due to something called the Somogyi effect, which is caused by rebound hyperglycemia after an episode of hypoglycemia while you are sleeping. Most common in people with type 1 diabetes, this can happen if you take long-acting insulin. It can also happen if you didn't eat a snack before bed. In either case, your blood sugar drops during the night and your body releases hormones to counteract the drop. The result? You wake up with a higher-than-normal blood glucose level.

Somogyi Effect

The Dawn Phenomenon

Another cause of high morning blood sugar is the "dawn phenomenon." In the dawn phenomenon, your body releases hormones that trigger your liver to put out glucose while you sleep. If there is not enough insulin in the body to counteract this, then blood glucose levels rise during the night, resulting in a high reading in the morning.

Further Explanation of Dawn Phenomenon

How to Tell the Difference

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 These Events

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.

Additional Ways to Combat Dawn Phenomenon

If the dawn phenomenon is causing your morning blood sugars to rise, then try these additional tips to counteract it:

  • Exercising in the evening may help keep morning blood sugars in a better range.
  • Eat breakfast, even if your blood sugar is high. Eating something will actually shut down the dawn phenomenon process and let your blood sugar return to normal.


"The Dawn Phenomenon." DOC News. 01 Jul 2006. Volume 3 Number 7 p. 5 American Diabetes Association. 24 Nov 2007.

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