Dawn Phenomenon vs. Somogyi Effect: Morning High Blood Sugars Explained

Ever go to bed with your blood sugar looking good, only to wake up with much higher blood sugar than you expected? As frustrating as this may be, it can more than likely be explained by the Dawn Phenomenon or Somogyi Effect.

What is the Dawn Phenomenon?

Everyone has an internal body clock that helps them wake up in the morning and sleep at night.

When the sun starts to rise, your body releases special chemicals (hormones) to help you wake up and get ready for the day. These hormones tell your liver to release sugar into your blood for energy.

If you have diabetes, your body has trouble handling this extra sugar, which can make your blood sugar go higher than normal in the early morning.

This is known as the Dawn Phenomenon.

What is the Somogyi Effect?

Another cause of higher morning readings is the opposite of the Dawn Phenomenon, and it’s called the Somogyi Effect.

The end result, however, is the same: higher than expected blood sugars in the morning.

In this case, the cause of the rise in blood sugar in the morning is the result of having a low blood sugar overnight, known as “nocturnal hypoglycemia.”

Symptoms of nocturnal hypoglycemia may include

• Restless sleep
• Nightmares and
• Sweating.

This can happen if you have too much long-acting insulin or if you exercised a lot. When your blood sugar gets too low, your body tries to fix it by releasing the same hormones that cause the Dawn Phenomenon. But instead of just waking you up, these hormones make your blood sugar go up too much.

Some people call this a “rebound” high blood sugar because your body is trying to bring your sugar back to a safe level but ends up raising it too high.

The best way to find out is to do some overnight monitoring. Here are some overnight monitoring tips steps to identify if your high morning blood glucose is due to the Dawn Phenomenon or Somogyi Effect: 

• Start your overnight checks at least three-to-four hours after your last meal
• Refrain from eating during the overnight check unless you need to treat a low blood sugar. Avoid drinking alcohol. 
• In the middle of your sleeping cycle. For example, if you sleep from 11pm to 7am, you would check around 3am. If you skip this step, you will not have enough information to sort out what is happening.  
• If you use a continuous glucose monitor, check your overnight history in the morning  

The results of your overnight check should reveal whether you are experiencing the dawn or the Somogyi effect. You may need to repeat your overnight monitoring one or two times to confirm.

                                                                                   Dawn Phenomenon vs. Somogyi Effect

How to Correct High Morning Blood Sugar

Because the causes of the Dawn Phenomenon and Somogyi effects are different, your problem-solving approaches for both of them need to be different. Here are some approaches to solve your morning highs: 

For the Dawn Phenomenon:

Try a bedtime snack: It is reasonable to experiment with having a bedtime snack to see if it helps prevent the unexpected rise later in the morning. You can also experiment with the type of snack, altering the amounts of fats, carbohydrates, and proteins to see if the effects are different. 

Eat regularly: Don’t go for more than six hours without eating. The longer you go without eating, the more likely your body will perceive this as a problem and try to use its own energy stores, which contributes to the higher readings.

Eat dinner earlier: Lengthening the amount of time between dinner and bedtime gives your body more time to get your blood sugar down after eating. Eat dinner earlier if you can. 

Be active after dinner: Any activity helps to lower blood sugar. Do a light physical activity after dinner may be helpful.

Take medications consistently: Some diabetes medications that are commonly prescribed act by helping with the rise in blood sugar from hormone effects overnight, so being sure not to miss any medication doses will help. Set an alarm if you need help remembering.

Discuss your medication timing and dosage with your provider: Ask if the timing of your medications in relation to your meals is optimal. There may be an option to move a dose that helps with the Dawn Phenomenon. If you are using an insulin pump, your overnight basal rate can be adjusted to blunt the rises in blood sugar in the early morning hours. Your morning dose of medication may be increased to account for this rise in morning blood sugar.

For the Somogyi Effect

Count carbs: Be as consistent as possible with your carb servings at night.

Eat regularly: Skipping meals can lead to low blood sugar if you are taking diabetes medications.

Avoid alcohol, but if you drink it be sure to eat a snack: Some people are very sensitive to alcohol and may need to eliminate or reduce it to avoid low blood sugars. Drink in moderation.

Think about the timing of your activity/exercise: Is evening activity causing your blood sugar to go low overnight? If so, work out earlier in the day.

Adjust insulin to carb ratio: If you are carb counting, you may need to consult your diabetes care team to better match your meal insulin to your carb amounts.

Discuss your medication timing and dosage with your provider: It’s important to understand the actions and effects of all of your diabetes medications and take them at the recommended times. If you take basal insulin, you may need to discuss adjusting your dose with your healthcare team.

For more information on how a Diabetes Care and Education Specialist can help you manage your blood sugar, visit diabeteseducator.org/DCEShelp.

This content was produced in partnership with the Association of Diabetes Care and Education Specialists (ADCES), a Founding Partner of Beyond Type 2.