The dawn phenomenon is an early-morning rise in blood sugar, also called blood glucose, in people with diabetes. The dawn phenomenon leads to high levels of blood sugar, a condition called hyperglycemia. It usually happens between 4 a.m. and 8 a.m.

The cause of the dawn phenomenon isn't clear. Some researchers believe the overnight release of certain hormones that happens naturally increases insulin resistance. That causes blood sugar to rise. The hormones are called counter-regulatory hormones because they have an effect that opposes the effect of insulin. They include growth hormone, cortisol, glucagon and epinephrine.

High blood sugar in the morning may be caused by:

• Not getting enough insulin the night before.
• Not getting the right dose of diabetes medicine the night before.
• Eating a snack with carbohydrates in it at bedtime.

If your blood sugar is consistently higher than it should be in the morning, talk to your health care provider. Your provider may suggest that you check your blood sugar once during the early-morning hours for a few days in a row. Or you might use a continuous glucose monitor to keep track of your blood sugar level as you sleep. That information helps your health care provider confirm if you have the dawn phenomenon or if there could be another reason for high morning blood sugar.

What you can do

To help you prevent or correct high blood sugar in the morning, your health care provider may suggest that you:

• Avoid carbohydrates at bedtime.
• Change your dose of diabetes medicine or insulin.
• Switch to a different diabetes medicine.
• Change the time when you take your medication or insulin from dinnertime to bedtime.
• Use an insulin pump to give you extra insulin during early-morning hours.