Diabetes: Morning High Blood Sugar Levels

For people taking insulin, blood sugars are often elevated in the morning. This is likely due to inadequate amounts of NPH/Lente insulin before dinner or at bedtime. High morning insulin is referred to as either the dawn phenomenon or the Somogyi effect.

• Dawn phenomenon. The dawn phenomenon is the end result of a combination of natural body changes that occur during the sleep cycle and can be explained as follows. Between 3:00 a.m. and 8:00 a.m., your body starts to increase the amounts of counterregulatory hormones (Growth hormone, cortisol and catecholamines). These hormones work against insulin's action to drop blood sugars. The increased release of these counterregulatory hormones, at a time when bedtime insulin is wearing out, results in an increase in blood sugars. These combined events cause your body's blood sugar levels to rise in the morning (at "dawn").
• Somogyi effect. Named after the doctor who first wrote about it, this condition is also called "rebound hyperglycemia." Although the cascade of events and end result -- high blood sugar levels in the morning -- is the same as in the dawn phenomenon, the cause is more "man-made" (a result of poor diabetes management) in the Somogyi effect. The term refers to pattern of high morning sugars preceded by an episode of asymptomatic (without symptoms) hypoglycemia. Your blood sugar may drop too low in the middle of the night, so your body counters by releasing hormones to raise the sugar levels. This could happen if you took too much insulin earlier or if you did not have enough of a bedtime snack.

How Do You Determine Which of the Two Conditions Is Causing the High Blood Sugar Levels?

Your doctor will likely ask you to check your blood sugar levels between 2:00 a.m. and 3:00 a.m. for several nights in a row. If your blood sugar is consistently low during this time, the Somogyi effect is suspected (too much nighttime insulin or too small of a bedtime snack for the insulin given). If the blood sugar is normal or high during this time period, the dawn phenomenon (increases in counterregulatory hormone) is more likely to be the cause.

How Can This Situation Be Corrected?

Once you and your doctor determine how your blood sugar levels are behaving during the nighttime hours, he or she can advise you about the changes you need to make to better control them. Options that your doctor may discuss include:

• Changing the time you take the long-acting insulin in the evening so that its peak action occurs when your blood sugars start rising.
• Changing the type of insulin you take in the evening
• Taking extra insulin overnight if you find that overnight your blood sugars are progressively elevated. Here, the additional insulin would help lower high morning blood sugars.
• Switching to an insulin pump, which can be programmed to release additional insulin in the morning

Reviewed by Certified Diabetes Educators in the Department of Patient Education and Health Information and by physicians in the Department of Endocrinology at The Cleveland Clinic.