Why do I have high blood sugar levels in the morning?


Brian Wu | Medical News Today

Some people experience very high blood sugar levels in the morning. But what implications does this have for a person’s health?

There are two main causes of high blood sugar in the morning, the dawn phenomenon and the Somogyi effect

This article explores these two causes of high blood sugar levels in the morning. It also discusses what risk factors may cause people to experience them and gives practical advice around how to better manage blood sugar levels.

The dawn phenomenon

The dawn phenomenon has to do with natural body changes that occur during the sleep cycle:

Midnight – 3 a.m.

While most people are sleeping, their body has little need for insulin. During this period, however, any insulin that may have been taken during the evening causes the blood sugar levels to drop off drastically.

Between 3 – 8 a.m.

The body automatically begins to dish out stored sugar (glucose) in preparation for the upcoming day. In addition, hormones that actively reduce the body’s sensitivity to insulin are also being released.

During this time period, counter-regulatory hormones are being released. This can interfere with insulin, which may lead to a rise in blood sugar.

These include growth hormones, such as:

  • cortisol

  • glucagon

  • epinephrine

These events are all happening simultaneously as bedtime levels of insulin are beginning to taper off. Each of these events ultimately plays a part in causing blood sugar levels to rise at “dawn” or in the morning.

Who the dawn phenomenon affects

Although people with diabetes are generally more aware of the dawn phenomenon, it actually happens to everyone. However, it affects people with or without diabetes differently.

Typically, people who do not have diabetes tend not to notice these high blood sugar levels in the morning. This is because their body’s insulin responds and adjusts the levels accordingly, meaning there is no excess of glucose left in the blood.

However, people with diabetes are unable to control their insulin levels. As a result, they commonly experience an increase in their fasting blood sugar levels.

Just as with anything else, the overall effects of dawn phenomenon vary from person to person. No two people will respond to the dawn phenomenon in the same way.

Somogyi effect

Another cause of high blood sugar levels in the morning is called the Somogyi effect or rebound hyperglycemia.

The Somogyi effect is not as common as the dawn phenomenon. It is named after the researcher Michael Somogyi who discovered it.

The reasons for the high blood sugar levels in the morning are the same for both the dawn phenomenon and the Somogyi effect.

There is one main difference between the two effects:

  • the dawn phenomenon occurs naturally

  • the Somogyi effect occurs as a result of poor diabetes management

Typically, ill-timed insulin or missed meals or snacks are the culprits. There are generally two different scenarios that can bring on the Somogyi effect:

  • Too much insulin, or not enough food before bed: During the night, a person’s blood sugar may drop too low. The body responds by releasing hormones to raise the sugar levels.

  • Insufficient insulin dose in the evening: In some cases, the person’s dose of insulin may not be sufficient, causing the person to wake up with a high morning blood sugar.

Testing for the dawn phenomenon and Somogyi effect

As the dawn phenomenon and the Somogyi effect are very similar, it is important for the doctor to determine which one a person has.

Doctors typically start by having people test their blood sugar levels for several nights in a row, usually between 2-3 a.m. A continuous blood glucose monitor is ideal for the job, but a regular glucose meter also works well.

If the person’s blood sugar is determined to be consistently low, this is typically deemed to be the Somogyi effect. If blood sugar levels are normal or continuously high when tested, this is more likely to be the dawn phenomenon.

Treatment options

Treatment for dawn phenomenon depends largely on how high the insulin levels are. There are a few things that a doctor may recommend to help, including:

  • avoiding eating a heavy amount of carbohydrates before bed

  • adjusting the doses of the insulin or other diabetic medication

  • switching to a different medication

  • changing the time a person takes long-acting insulin in the evening

  • using an insulin pump may help to regulate the insulin dosage

Some of the same options can be used to treat both the Somogyi effect and the dawn phenomenon. However, some of the recommendations for people experiencing the Somogyi effect differ.

Recommendations include:

  • eating a carbohydrate snack at least a few hours before bedtime

  • seeing a doctor about reducing blood sugar-lowering medication doses in the evening

  • reducing long-acting insulin doses


For most people, dawn phenomenon is short-lived and does not cause a lot of problems. For people who only experience a slight increase in blood sugars in the morning, the effects are generally short-lived.

Impact of insulin resistance

Some people are prone to be more resistant to insulin in the morning. As such, limiting carbohydrates when first waking up is recommended.

Until they eat, some people do have problems with their blood sugar continuing to rise in the morning. These people, therefore, spend an extended period with high blood sugar levels. This can be dangerous and should be watched closely. They should see a doctor help get their condition under control.

Impact of changes in hormones

If the Somogyi effect is ignored, complications may occur over time. As the body’s hormones change, a person’s response to low blood sugar may also change. This may leave the body unable to adequately readjust to low blood sugar.

Although there may not be any noticeable symptoms, the body may become unable to signal to the liver to dump sugar into the blood.

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