The Dawn Phenomenon: What It Is and How to Fix It

The Reason Your Blood Sugar Could Be Elevated in the Morning

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The dawn phenomenon is a surge in hormones that causes blood sugar levels to be elevated in the morning—even before you've eaten anything. Anyone can experience this type of hormonally generated hyperglycemia, even people who don't have diabetes, but no matter your health status, the dawn phenomenon can be prevented.

Woman waking up in bed

LWA / Dann Tardif / Blend Images / Getty Images 

Causes

Again, the dawn phenomenon can affect anyone. However, according to research from the American Diabetes Association, it may be particularly problematic for people who have diabetes. This is because their bodies are not able to respond normally to the blood sugar increase, which may in turn allow their glucose to reach especially high levels.

At night the body naturally produces less insulin. But during the last hours of sleep, from around 4 a.m. to 8 a.m., hormones tied to the circadian rhythm start to trigger the circulation of glucose throughout the body to provide energy for cells to use for the day ahead. Hormones such as cortisol, adrenaline, glucagon, and growth hormone each trigger the body to pump out more glucose from the liver and muscles, but this, combined with the lack of insulin in circulation, results in a natural blood sugar rise in the morning.

While the dawn phenomenon is normal for most people, it can be amplified in those with diabetes who have greater insulin resistance. If you suddenly realize your fasting morning glucose is soaring, it could be related to not taking an adequate dose of insulin at night, missing your evening diabetes medication, or overeating carbohydrates at dinner or bedtime.

Treatment

The hormones causing glucose to increase can make morning glucose tougher to treat in people with diabetes, but you can take steps to counteract the dawn phenomenon, such as:

  • Increasing or changing the timing of medication: Increasing medication, making sure you aren't missing doses, or taking your meds at a different time may help lower your morning blood sugar. Discuss these options with your doctor before making any changes.
  • Reduce evening carb intake: Cutting back on carbs (at least during dinner and evening hours) could help you prevent a morning glucose burst.
  • Exercise in the evening: Going for an after-dinner walk, bike ride, or jog may help keep morning blood sugars in a better range.
  • Skip the late-night snack: If you're truly hungry, choose something fat- and protein-based that won't raise your glucose much, like nuts or cheese.
  • Get a good night's sleep: Aim for six to eight hours each night, as fewer than six hours of sleep has been shown to significantly raise blood sugar levels.
  • Eat breakfast: Even if your blood sugar is high, eating something will actually shut down the dawn phenomenon process and help your blood sugar return to normal.
  • Test regularly: The only way to know what's normal for your body is to frequently test your blood sugar. As the level will fluctuate throughout the day, a slight elevation may not be too far out of the ordinary for you.

Check your eligibility for a continuous glucose monitor (CGM)—a small device that measures real-time glucose 24 hours a day. Alarms can sound off when your blood sugar is trending high or low, even at night.

The Somogyi Effect

Occasionally, though less often, the problem of elevated morning fasting glucose may be due to something called the Somogyi effect, which is caused by rebound hyperglycemia (high blood sugar) after an episode of hypoglycemia (low blood sugar) while you are sleeping. Most common in people with type 1 diabetes, this can happen if you take nightly insulin. The Somogyi effect seems to occur more often in those on higher doses of insulin. 

It can also happen if you take insulin and your bedtime blood sugar was on the lower side and you didn't eat a snack before bed. In either case, your blood sugar drops during the night and your body releases hormones to counteract the drop. The result? You wake up with a higher than normal blood glucose level.

If you have type 1 diabetes and are experiencing this effect, let your doctor know. They may need to change your medication or insulin dosages.

If you are taking insulin, monitor your blood sugar before you go to bed. If your levels are too low—for example, less than 100 mg/dL (though this can vary for each person)—you may need to have a snack before bed consisting of some protein, fat, and a small number of carbohydrates. For example, a handful of berries and plain Greek yogurt or half a nut butter sandwich on whole-grain bread. 

How to Tell the Difference

The best way to know for sure whether you're experiencing the dawn phenomenon or the Somogyi effect is to test your blood sugar in the middle of the night. Wake up sometime between 2 a.m. and 3 a.m. for several nights in a row and check your blood sugar. If you are low at that time (less than 70 mg/dL), it could be the Somogyi effect. If you are normal or high, then the dawn phenomenon may be the culprit. You'd need to do this a few nights in a row to determine whether or not this has become a pattern warranting a change or if it was just a fluke episode.

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