Sometimes diabetes doesn’t make a whole lot of sense. Take those mornings when you wake up with blood glucose that’s higher than it was when you went to sleep. You’d think that not eating for those seven or eight hours would give you lower blood glucose. But in fact, there are three reasons your blood glucose may be higher in the morning: the dawn phenomenon, the Somogyi effect, or waning insulin.

The Dawn Phenomenon

The dawn phenomenon is a natural rise in blood glucose between the hours of 4:00 a.m. and 8:00 a.m., and it occurs because of hormonal changes in the body. “The body does several things to get ready for the day,” says David S. Schade, MD, professor of medicine and chief of the Division of Endocrinology at the University of New Mexico School of Medicine in Albuquerque. “The body releases hormones like cortisol and growth hormone and the blood glucose rises. People without diabetes just secrete more insulin to handle the blood glucose, but for people with diabetes, the rise in blood glucose can be substantial.”

Schade notes that the effects of dawn phenomenon vary in each person, and your blood glucose may be higher on some mornings than on others. “You can do the same exercise and eat the same thing every day and have different blood glucose [levels] on different mornings because of dawn phenomenon,” he says. “That makes it a little problematic.”

He adds that the scientific community is still figuring out the relationship between the release of these hormones and the rise in blood glucose. However, one thing scientists do know is that the liver produces glucose as part of the dawn phenomenon.

Treatment for dawn phenomenon depends on how you treat your diabetes, says Stuart T. Haines, PharmD, BCPS, professor and pharmacotherapy specialist at the University of Maryland School of Pharmacy in Baltimore. If you take insulin, you may be able to adjust your dosing so that peak action occurs closer to the morning rise in your blood glucose. If you have type 2, diabetes pills provide options as well, he says: “You can add metformin to reduce the liver’s glucose production.”

The Somogyi Effect

The Somogyi effect, named for researcher Michael Somogyi, PhD, who studied and first described it, is your body’s response to a low that you had while you were sleeping. “This happens after low blood glucose induced by excess insulin, alcohol consumption, or not having had enough food,” says Haines. “You have a low, and to counter that, your body responds in a rigorous way and cranks out a bunch of hormones, like glucagon.” The body responds to those hormones by raising blood glucose—sometimes too much.

You would treat this the opposite way of how you would treat dawn phenomenon, says Schade. “You could have a snack before you go to sleep or reduce your insulin infusion at night. If you take NPH, you can switch to an insulin that won’t dip you down at 3:00 a.m.”

But wouldn’t a low wake you up? Not necessarily, says Mindy Saenz, RD, LDN, CDE, clinical dietitian and diabetes educator in the Division of Endocrinology at the Brody School of Medicine at East Carolina University in Greenville, N.C. “You can sleep right through them,” she says. “Nighttime lows are the most dangerous.” She adds that it’s a good idea to check your blood glucose if you wake up sweating or with headaches, as those are signs of a low.

Waning Insulin

The dawn phenomenon and the Somogyi effect are pretty complicated hormonal stuff, but sometimes the simplest explanation is the correct one, Saenz says. Sometimes your insulin just runs out or wears off. Then it’s a matter of you and your doctor adjusting your insulin regimen accordingly. “If it’s insulin waning, you could look at splitting your basal insulin or taking it at a different time of the day,” she says. “If you take NPH at supper, you could move it closer to bedtime.”

Before you and your doctor can adjust your diet or medications to handle high morning blood glucose, you have to know which of the three potential causes is the culprit. Experts agree that there’s one simple, if somewhat inconvenient, way of figuring out what that might be: Check your blood glucose at 3:00 a.m. for several nights in a row. “You need to see where your blood glucose is at bedtime, at 3:00 a.m., and in the morning,” says Saenz. She explains it this way:

• If your blood glucose is fairly even between bedtime and 3:00 a.m., but then rises between 3:00 a.m. and morning, chances are you’re experiencing dawn phenomenon.
• If your blood glucose is low at 3:00 a.m., you’re most likely experiencing the Somogyi effect.
• If your blood glucose is higher at 3:00 a.m. than at bedtime and higher still in the morning, your insulin is probably waning.

A continuous blood glucose monitor can go a long way toward helping you nab the perpetrator. These monitors record your blood glucose every few minutes around the clock, and they have alarms to alert you to highs and lows. The problem is that these monitors are expensive, and insurance coverage for them is hard to come by, says Schade. “We’re all trying to get insurance to cover them, and some plans will, but Medicare won’t,” he says. “Some insurance companies will cover them if your doctor fills out a special form indicating why one would help you, but it’s sporadic so check with your insurance company and see what the criteria are.”

If you have diabetes, chances are you’ll experience the occasional high morning blood glucose. That’s not something to fret about too much. But if it happens regularly, then it’s time to call your doctor. “You should also suspect a problem when your morning blood glucose is the highest of the day, and when it is consistently high for the rest of the day after that,” says Haines. Schade agrees. “If it’s significant, it should be dealt with because those who have high blood glucose in the morning tend to have high blood glucose all day,” he says. “It’s important to recognize that and adopt a strategy to control it.”

Terri D’Arrigo is a writer living in Holbrook, N.Y.