Diabetes Forecast

Handling Morning Highs in Blood Glucose

By Erika Gebel, PhD , ,

You wake up to find your blood glucose looking as if you've been up all night eating cookies. What's going on? Such morning highs are common in people with diabetes, but there are ways to get those numbers down and to start more days comfortably in range.

Overproductive Liver

There are two processes that can trigger morning highs: the dawn effect (or dawn phenomenon) and waning insulin. A third possibility, the Somogyi effect, may lead to morning highs, but whether or not this actually occurs is controversial.

Whatever the cause of morning highs, the source of the excess glucose is the same: the liver, the body's glucose storehouse and production center. Hormones signal the liver to keep the body fueled by releasing glucose into the blood between meals and overnight. Hormone imbalances in diabetes of any type—too little insulin made by the body or taken as medication and too much of the hormones that counteract insulin—can send the wrong signal and cause the liver to pump out more glucose than it should.

Dawn Effect

The dawn phenomenon is a rise in blood glucose that occurs in the early morning hours, usually between 3 and 6 a.m. in people with a typical sleep schedule. The dawn effect is thought to be triggered by a normal predawn increase in the levels of hormones, particularly human growth hormone, that tell the liver to release glucose. This is the body's way of making sure it has enough energy to get up and go come dawn. People with diabetes, though, may not have enough insulin to counteract these hormones. So a delicate balance is lost, and blood glucose can be too high by morning.

Many people assume that the culprit behind a morning high is dinner the night before, but it may be the dawn effect that's to blame. Eating breakfast helps to normalize blood glucose levels; it signals to the body that it is day and time to rein in the anti-insulin hormones.

Waning Insulin

It is possible that an evening meal could lead to higher than normal blood glucose levels the morning after, but in that case the cause may be too little mealtime insulin, waning long-acting insulin from an evening injection, or not enough overnight basal insulin through a pump. If an evening insulin dose (or overnight basal pump rate) is insufficient, blood glucose levels may creep up as you sleep. With waning insulin, the rise in blood glucose is typically more gradual than with the dawn effect.

Somogyi Effect

The Somogyi effect is often called a "hypoglycemic rebound," though researchers still debate its existence. The theory is that if a person with diabetes experiences hypoglycemia overnight (which could have been triggered by taking too much medicine, eating too little, or drinking alcohol), the body deploys anti-insulin hormones to bring blood glucose levels back up. The body can overdo it, however, leading to morning highs.

What's Behind Your High?

Here is how to do some detective work about likely causes of morning highs. For three days (in a row or pick random days), plan specific blood glucose tests. Check your blood glucose at bedtime, wake up about 3 a.m. to check again, and take a final reading at your normal wake-up time. Comparing any significant changes at the various times can help tell you and your health care provider what's to blame for morning highs. A continuous glucose monitor is also a good tool for figuring out what blood glucose is up to overnight—some clinics will set you up with a loaner device for three days or so of intensive blood glucose testing.

Blood Glucose Detective
Use this chart of blood glucose levels to help determine the cause of morning highs.
Bedtime 3 a.m. Morning Likely Culprit
Normal Normal High Dawn Effect/Waning Insulin
Normal High Higher Waning Insulin
Normal Low High Somogyi Effect

What Else Can You Do?

Most people with diabetes have a morning high once in awhile, but if it becomes a regular occurrence, talk to your doctor about whether your medication needs adjustment. Subtle changes can help you deal with your body's changing insulin needs overnight. While there is little research on how best to combat morning highs, here are some other things you may want to consider.

All Morning Highs

  • With the help of a provider, modify your medication regimen.
  • For pumpers, especially people with type 1 diabetes, basal rates can be fine-tuned to deal with varying insulin needs overnight.
  • Ask your health care provider for recommendations on using physical activity to help control blood glucose levels.

Somogyi Effect

  • Eat a snack with some carbohydrate and protein before bed.
  • Discuss with your doctor a safe, slightly higher target blood glucose range for bedtime.


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