Dawn Phenomenon

Dawn Phenomenon


Dawn phenomenon is a rise in glucose (blood sugar) in the early morning. This occurs naturally in everybody, but in people with diabetes it can result in abnormally high glucose (hyperglycemia).

Dawn phenomenon usually occurs between 4 a.m. and 8 a.m. Overnight the body releases a group of hormones known as counterregulatory hormones. These natural chemicals signal the liver to release glucose into the bloodstream and suppress the activity of insulin, causing glucose levels to rise.

In most people, glucose rises just enough to provide the body with the energy necessary to wake up and begin the day. A burst of insulin handles any excess glucose. However, people with diabetes either do not produce insulin (type 1 diabetes) or cannot properly use available insulin (type 2 diabetes) to respond to this rise in glucose. As a result, glucose continues to rise and causes hyperglycemia.

To adapt to dawn phenomenon, patients may be advised by their physician to make changes in their treatment plan such as adjusting their diet, glucose monitoring, medication or exercise.

About dawn phenomenon

Dawn phenomenon is a normal early-morning rise in glucose (blood sugar) that occurs before or shortly after waking. Everybody experiences this physiological phenomenon, but it can be troublesome for people with diabetes. Such patients may need to adjust their treatment regimen to account for dawn phenomenon, as advised by their physician.

Between 4 a.m. and 8 a.m., the body increases the production of counterregulatory hormones. These natural body chemicals suppress the activity of insulin, a hormone that transports glucose into cells to use for energy. The counterregulatory hormones include:

  • Growth hormone
  • Cortisol
  • Catecholamines
  • Glucagon
  • Epinephrine (adrenaline)

Counterregulatory hormones trigger the liver to release enough glucose from glycogen to give the body the energy to wake up. In nondiabetic people, the body responds to the excess glucose that accumulates as a result of this process by producing insulin. The insulin then moves the excess glucose into the cells.

However, patients with diabetes either fail to produce insulin (type 1 diabetes) or cannot properly use the insulin that is available (type 2 diabetes). As a result, glucose continues to rise to abnormally high levels (hyperglycemia).

The effect of dawn phenomenon on diabetic patients varies. Some patients are strongly affected and have very high glucose on wakening, but others are weakly affected. In addition, some patients with dawn phenomenon find that their glucose continues to rise until they eat in the morning. For others, levels will settle down a few hours after waking, regardless of whether or not they eat.

In some cases, high glucose in the morning may be the result of factors other than dawn phenomenon. For example, during sleep people experience falling glucose levels because of the lack of food overnight. To compensate, the body may produce a “rebound effect” response that increases the liver’s production of glucose to levels that are abnormally high. This is known as rebound hyperglycemia, or Somogyi effect.

People who experience symptoms may need to perform glucose monitoring in the middle of the night to distinguish between dawn phenomenon and rebound hyperglycemia. Patients may be advised by their physicians to test their glucose around 4 a.m. and compare it to their waking glucose level. If glucose is low in the first reading and high in the second, Somogyi effect is likely at work.

Symptoms and diagnosis

Patients who experience dawn phenomenon are unlikely to detect any symptoms associated with the condition. The condition may reveal itself only after patients test their glucose(blood sugar) in the morning and find levels to be high.

In diagnosing dawn phenomenon, a physician is likely to perform a physical examination and obtain a medical history and list of symptoms.

If dawn phenomenon or the Somogyi effect is suspected, the patient may be asked to perform glucose monitoring between 2 a.m. and 3 a.m. for several consecutive nights. If glucose in these blood samples is consistently normal or high, dawn phenomenon is the likely culprit. If glucose readings indicate nocturnal hypoglycemia, which is followed by morning hyperglycemia, the Somogyi effect is indicated.

Patients should consult a physician about how to treat bouts of overnight hypoglycemia, morning hyperglycemia or other problems with glucose control. Changes in diet, exercise regimen, insulin therapy or other medication may be necessary.

Treatment and prevention

Diabetic individuals who need treatment for dawn phenomenon should consult their physician about the best treatment for them. Depending on the case, options may involve adjusting the pre-bedtime diet, exercise plan, antidiabetic agents or insulin therapy. The variation in the effect of dawn phenomenon from one individual to another may require differences in how people control glucose (blood sugar). Possible changes may include:

  • Adjusting insulin dosage. Physicians may recommend that patients take more insulin in the evening or schedule their dosages of long-acting insulin later in the evening so peak action occurs when glucose starts rising.
  • Using an insulin pump. Patients who use an insulin pump to deliver their medication can program the device to deliver a higher dose of insulin in the early morning.
  • Eating a snack before bedtime. Some patients may be advised not to eat late at night. However, some cases of dawn phenomenon are a response to lower glucose that occurred earlier. Their physicians may advise such patients to smooth these glucose roller coasters by eating a snack before bedtime. They may recommend a small snack that contains protein or fat and is low in carbohydrates, such as nuts or cheese.
  • Exercising earlier in the day. Strenuous physical activity at night can cause nocturnal hypoglycemia, which may trigger rebound hyperglycemia.
  • Taking metformin. This antidiabetic agent curbs glucose production by the liver, and has been used effectively to treat patients with dawn phenomenon.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about dawn phenomenon:

  1. How do I know if I have dawn phenomenon? Are there any symptoms I should look for?
  2. What tests might I need to have for dawn phenomenon? If I need to check my glucose in the early morning, at what hour should I do this, and for how many nights?
  3. What do my test results indicate?
  4. How does dawn phenomenon affect my blood sugar and diabetes management plan?
  5. What are my treatment options for dawn phenomenon?
  6. Should I have a snack before bedtime? If so, how much should I eat, and what type of food?
  7. Should I exercise in the morning or afternoon rather than at night?
  8. Can I do anything else to prevent dawn phenomenon?
  9. Can dawn phenomenon be harmful in people who have prediabetes or normal glucose?
  10. How does it differ from the Somogyi effect? Do I have any signs of the Somogyi effect? If so, how will this be treated?
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