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.

The Most Likely Culprit

The most likely cause of high morning glucose is not taking an adequate dose of insulin at night, missing your evening diabetes medication or overeating carbohydrates at dinner or bedtime. This can be complicated by counter-regulatory hormones, which can rise in the early morning and make morning glucose tougher to treat. If this is the problem, you may need more medication (if you aren't missing doses) or less carbohydrates at night. Sometimes, changing the timing of your medication can also help to reduce morning blood sugars. 

Somogyi Effect

Much less often the problem may be due to something called the Somogyi effect, which is caused by rebound hyperglycemia (high blood sugar) after an episode of hypoglycemia (low blood sugar) while you are sleeping. Sometimes seen in people with type 1 diabetes, this can happen in people who take nightly insulin, especially higher doses of insulin. If insulin causes the blood sugar to drop during the night, hormones may be released to counteract the drop. This can result in higher than normal blood glucose levels in the morning.

While in the past the Somogyi effect was thought to occur fairly commonly, it is now thought to be a rare phenomenon. Much more common is the "dawn phenomenon."

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.

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 3 and 5 a.m. for several nights in a row, and check your blood sugar. If you are low at that time (<70mg/dL), it could be the Somogyi effect. If you are normal or high, then the dawn phenomenon may be the culprit. You need to do this a few nights in a row to determine whether or not this has become a patter that warrants a change or if it was juke a fluke episode.

How to Counteract These Events

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

  • If you are taking insulin, monitor your blood sugars before you go to bed. If you are too low, for example, less than 100 mg/dL (each reference range is different for individuals), you may need 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. Keep a log of your medicine, food and morning blood sugars for a few days so that you can pattern manage. This information is extremely useful in trying to figure out what is happening. Your doctor can use it to make changes in your medicine, insulin dosages, the timing of your medicine, exercise regimen, or meal plan. 

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.
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Article Sources
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  2. Blood Sugar: Hidden Causes of High Blood Sugar Levels in the Morning. Cleveland Clinic. May 2018.

  3. A Diet Tip for People With Type 2 Diabetes: Eat More Nuts. Cleveland Clinic. May 2019.

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