What Causes High Blood Sugar in the Morning?

Medically Reviewed By Marina Basina, M.D.

High blood sugar in the morning may result from factors like the dawn phenomenon, waning insulin, or obstructive sleep apnea. You may need to wear a continuous glucose monitor or record your blood sugar levels at certain intervals around your sleep to determine the underlying cause. Although it may not be a concern if it occurs only occasionally, consistently high glucose levels upon waking need your doctor’s attention. They can help you identify the cause and recommend treatment.

This article discusses a few possible causes of high blood sugar when waking up. 

Dawn phenomenon

An adult female waking up in bed
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The “dawn phenomenon” describes high morning glucose due to a natural rise in hormone levels. During the early morning hours, your body releases cortisol and growth hormones to prepare for the day.

Your liver produces extra glucose in response to these hormones. For people without diabetes, the body secretes more insulin to handle the excess glucose. But for people with diabetes, the body can’t produce enough insulin Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source , and blood glucose levels can rise too high.

Increased blood sugar due to the dawn phenomenon is usually treated with insulin or medications like metformin (Fortamet). If you are already on insulin, the type of insulin you’re taking or your dosage may need to be changed.

Some research has shown Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source that moderate physical activity before eating your first meal of the day may also help reduce elevated glucose levels.

Learn 12 signs of uncontrolled diabetes.

The Somogyi effect

Named after the scientist who first described the condition, the Somogyi effect refers to the body’s production of excessive glucose in response to a period of low glucose, or hypoglycemia, during sleep. This differentiates it Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source from the dawn phenomenon, which doesn’t occur secondary to hypoglycemia.

Though this phenomenon was commonly suggested as a cause of morning hyperglycemia, recent research Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source hasn’t found definitive evidence to back it up. More studies are needed to determine whether the Somogyi effect occurs and, if so, what causes it.

Obstructive sleep apnea

Obstructive sleep apnea (OSA), a condition in which your airways become intermittently obstructed during sleep, is common Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source in people with type 2 diabetes. The two conditions can influence each other, with OSA contributing to developing type 2 diabetes and type 2 diabetes negatively affecting the airways during sleep.

Although the exact underlying mechanisms aren’t clear, research from 2020 Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source showed that people with moderate to severe OSA experienced increasing glucose levels during sleep. People with no or mild OSA experienced decreasing glucose levels.

More research is necessary to determine how OSA and diabetes influence each other and if treatments for one condition may improve the other. However, maintaining a moderate weight and managing OSA with treatments like a continuous positive airway pressure (CPAP) machine may help manage Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source blood sugar levels.

Learn 12 things your diabetes doctor wants you to know.

Waning insulin

According to the American Diabetes Association (ADA), if you take insulin and have been experiencing high blood sugar in the morning, your insulin may be wearing off too soon. If this is the case, your doctor may adjust your dosage or change the time you take the insulin to prevent high glucose levels.

Pinpointing the cause for effective treatment

Understanding what’s causing your morning hyperglycemia is essential before your doctor can recommend the appropriate treatment.

To pinpoint the cause, your doctor may ask you to check and record your blood glucose levels before bed, during your sleeping period, and first thing when you wake up. A continuous glucose monitor can also help record your blood glucose levels without interrupting sleep.

Once you’ve identified the cause, ask your doctor about a treatment plan to manage it.

Read 5 tips for monitoring your blood sugar.

Summary

High blood sugar upon waking may be caused by a few factors, such as waning insulin levels or the effects of OSA. Your doctor may ask you to record your blood sugar levels before, during, and after your sleeping period to pinpoint the cause.

Talk with your doctor if you’re experiencing high blood sugar in the morning.

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Medical Reviewer: Marina Basina, M.D.
Last Review Date: 2023 Aug 15
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