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Diabetes Health Center

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Why Is My Blood Sugar High in the Morning?

Do you take insulin for diabetes and have high blood sugar levels in the morning? It happens to a lot of people, and there are solutions -- once you know why it’s happening.

Doctors have narrowed down the reasons for this to two different causes.

The dawn phenomenon. This is the result of several natural body changes that happen while you’re asleep. Between 3 a.m. and 8 a.m., your body starts to ramp up the amounts of certain hormones that work against insulin's action to drop blood sugar levels. They enter your system just as your bedtime insulin is wearing out and sugar levels rise.

The Somogyi effect. Named after the doctor who first wrote about it, doctors also call this "rebound hyperglycemia." The term refers to pattern of your blood sugar being high in the morning, after having been low (hypoglycemia). Usually there are no symptoms, but night sweats can be a sign.

Your blood sugar may drop too low in the middle of the night. In response, your body releases hormones to raise it. This could happen if you took too much insulin earlier or if you didn’t have enough of a bedtime snack.

To learn the reason for your high morning blood sugar, your doctor will likely ask you to check your levels between 2 a.m. and 3 a.m. for a few nights in a row.

If it’s consistently low during this time, the Somogyi effect is probably the cause. If it’s normal or high during this time period, the dawn phenomenon is more likely the reason.

How Do I Treat It?

Once you and your doctor figure out how your blood sugar levels behave overnight, she may suggest changes like these:

  • Change the type of insulin so it doesn’t peak at the wrong time or in the middle of the night.
  • Take extra insulin overnight if your blood sugar goes up during the evening.
  • Switch to an insulin pump, which can be programmed to the release the amount of insulin you need during the problem time periods.

WebMD Medical Reference

Reviewed by Brunilda Nazario, MD on September 11, 2015

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