When you check your blood sugar just before breakfast, it should normally be fairly low after a long night without food. However, some diabetics notice morning hyperglycemia, or high blood sugar, and aren't sure why. This phenomenon can occur in both type 1 and type 2 diabetics, with over 50 percent of both types affected, according to a January 2005 review article in "Endocrine Practice."
The Dawn Phenomenon
Dawn phenomenon is the term used to describe an abnormal early-morning increase in blood sugar, or glucose, which usually occurs between 3 and 8 a.m. in people with diabetes. If you take insulin before bedtime, your blood sugar should be at its lowest point at about 3 a.m. and as such, your body responds by pumping extra glucose into your bloodstream to counteract the extremely low levels and provide fuel for your early morning activities. This release of blood sugar coincides with a release of hormones, including cortisol, glucagon and epinephrine, which all make your body more resistant to insulin and less able to clear excess glucose out of your bloodstream. When you are diabetic, your body's already poor control of blood sugar is hampered even further by these hormones. By the time you check your blood sugar just before eating breakfast, you may be experiencing hyperglycemia.
The Somogyi Effect
For some diabetics, the impact of the dawn phenomenon is increased by poor diabetes control, a condition called the Somogyi effect. There are two possible causes for this effect: If your insulin dose is too high just before bed or you don't have an adequate bedtime snack, your body could respond with an increased release in blood sugar. In diabetics who take long-lasting insulin before bed, the rise in blood sugar can also occur if the dose is not strong enough to last the whole night through. If your blood sugar is low between 2 and 3 a.m., several nights in a row, but you still experience hyperglycemia at breakfast, the Somogyi effect is probably to blame. If your blood sugar is already high at this point, you might be experiencing the dawn phenomenon.
Response
One way your doctor may help you deal with morning hyperglycemia is to change your long-lasting insulin dose so that your insulin levels peak when your blood sugar would normally be rising. Taking extra insulin overnight or taking insulin first thing in the morning are two other options your doctor might discuss with you. An insulin pump that delivers insulin while you sleep works well for some diabetics. Eating a heartier bedtime snack with fewer carbohydrates and more protein and fat might also help. If you cannot lower blood sugar significantly in the morning, you might have to eat a lighter breakfast while your body catches up.
Considerations
Getting morning blood glucose levels under control is vital for overall blood sugar control. Poor morning control can lead to difficulties maintaining your blood sugar during the remainder of the day and can cause difficulties in long-term control. If your blood sugar is typically high in the morning, talk to your doctor to determine and correct the underlying cause.
References
- Cleveland Clinic; What Causes High Blood Sugar Levels in the Morning?; February 2009
- MayoClinic.com; The Dawn Phenomenon: What Causes It?; Maria Collazo-Clavell, M.D.; Nov. 21, 2009
- "Endocrine Practice"; The Dawn Phenomena Revisited: Implications for Diabetes Therapy; M.F. Carroll, et al.; January 2005
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