What Causes High Blood Sugar in the Morning?


Quick Answer

There are two reasons that blood sugar rises in the morning,: the dawn phenomenon and the Somoyi effect, states the Cleveland Clinic. The latter is also referred to as rebound hyperglycemia.

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Full Answer

The dawn phenomenon is caused by a natural process, according to the Cleveland Clinic. When a person takes insulin taken before bed, this causes blood sugar to drop from midnight until 3 a.m. Between 3 a.m. and 8 a.m., the body prepares for the day by releasing stored glucose. During this time, hormones that reduce sensitivity to glucose levels are released. This happens as the insulin taken before bed is wearing off, causing a spike in blood sugar.

The Somoyi effect is much like the dawn phenomenon, but instead of a natural process, this type of spike in blood sugar results from poor diabetes management, states the Cleveland Clinic. Taking too much insulin or skipping a bedtime snack often causes blood sugar to drop too low during sleep. The body releases hormones to raise sugar levels in response, resulting in a blood sugar increase.

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