Dawn Phenomenon

Dawn phenomenon is a common cause of high blood sugar levels in the morning for people with diabetes. It’s due to a natural increase in certain hormones in the early morning hours. Treatment for dawn phenomenon varies depending on your existing diabetes management plan.


What is dawn phenomenon?

Dawn phenomenon happens when hormones your body naturally makes in the early morning increase your blood sugar. Dawn phenomenon only affects people with diabetes. It’s a common cause of high blood sugar (hyperglycemia) in the morning.

It’s important to remember that there are other possible causes of high blood sugar in the morning, such as:

  • Too little medication, which wears off overnight.
  • Miscalculating and mistiming your medication dose with your evening meal/food consumption.
  • The Somogyi (pronounced “so-MOH-gyee”) effect — when injected insulin lowers your blood sugar too much overnight, and your body responds by releasing hormones that cause your blood sugar to increase too much.

How common is dawn phenomenon?

Dawn phenomenon is common in people with diabetes. Studies show that it affects over 50% of people with Type 1 diabetes or Type 2 diabetes.


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Symptoms and Causes

What are the symptoms of dawn phenomenon?

The main sign of dawn phenomenon is high blood sugar in the early morning. You may find you have high blood sugar with a glucometer reading and/or through your continuous glucose monitoring (CGM) device when you wake up. Dawn phenomenon usually causes a pattern of high blood sugar levels over several mornings.

Depending on how elevated your blood sugar is, you may have the following symptoms when you wake up:

What causes dawn phenomenon?

In the early morning — between approximately 3 a.m. and 8 a.m. — your body releases a surge of hormones, including cortisol and growth hormone. These hormones signal your liver to boost its production of glucose, which provides energy that helps you wake up. This boost of glucose increases your blood sugar (glucose).

If you don’t have diabetes, your pancreas responds and releases an adequate amount of insulin to regulate your blood sugar. If you have diabetes, your pancreas either doesn’t make any or enough insulin to respond to the rise in blood sugar, resulting in high blood sugar. Insulin resistance can also contribute to this phenomenon.


Diagnosis and Tests

How is dawn phenomenon diagnosed?

The most effective way to diagnose or detect dawn phenomenon as the cause of elevated morning blood sugar is with continuous glucose monitoring (CGM).

CGM involves wearing a device that measures your glucose levels 24 hours a day. More specifically, a CGM device measures your levels every few minutes. The device uses this data to form a graph that shows a more complete picture of how your blood sugar levels change over time.

As opposed to manual finger-stick/glucometer checks before you go to sleep and after your wake up, using CGM ensures you haven’t experienced any overnight episodes of low blood sugar (hypoglycemia). This could indicate you’re experiencing the Somogyi effect rather than dawn phenomenon.

If you don’t use CGM, healthcare providers can usually still suspect dawn phenomenon by assessing patterns of consistent glucometer readings.

Management and Treatment

What is the treatment for dawn phenomenon?

The most effective treatment for combating dawn phenomenon is taking insulin with an insulin pump. Oral diabetes medications typically don’t help with dawn phenomenon. Long-acting insulin injections also can’t help.

Your healthcare provider can guide you on adjusting your basal rates and programming the pump to automatically deliver more insulin in the early morning hours. This can prevent your blood sugar levels from increasing.

If you don’t use an insulin pump or don’t take insulin, it may take trial and error before you and your provider figure out the best medication and lifestyle strategy to help combat morning high blood sugar due to dawn phenomenon. Your provider may recommend increasing the amount of exercise you do in the evening and increasing the protein-to-carbohydrate ratio of your evening meal, for example.

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Can I prevent dawn phenomenon?

As dawn phenomenon is the result of a natural body process, there’s nothing you can do to prevent it.

However, if you use an insulin pump, you may be able to prevent future episodes of high blood sugar due to dawn phenomenon by adjusting your basal rates with guidance from your provider.

Outlook / Prognosis

What are the complications of dawn phenomenon?

The main complication of untreated high blood sugar due to dawn phenomenon is an increase in A1C levels. An A1C test represents the average amount of glucose (sugar) in your blood over the past three months.

The higher your A1C levels, the more you’re at risk for developing complications, especially if they’re consistently high over several years. Diabetes complications include:

Studies show that people with diabetes may be able to reduce the risk of diabetes complications by consistently keeping their A1C levels below 7%.

As dawn phenomenon is usually a persistent issue, not addressing or treating it can lead to consistently high blood sugar for at least a few hours every day. This can increase your risk of diabetes complications over time.

Living With

When should I see my healthcare provider?

If you have consistently high blood sugar in the morning, it’s important to talk to your healthcare provider who helps you manage diabetes. They can assess your blood sugar readings to see if dawn phenomenon is the culprit and recommend treatment options.

A note from Cleveland Clinic

Experiencing dawn phenomenon and high morning blood sugars can be frustrating and annoying. Know that it’s not your fault. There’s no single way to anticipate and manage morning highs, so it may take time to find the best treatment strategy for you. Your healthcare provider can help you determine the best plan of action. Don’t hesitate to reach out to them for help. Taking action now can help you avoid long-term complications.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 12/20/2022.

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