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Understanding What Causes High Morning Glucose


This is not how you want to start the day: You wake up, check your blood glucose, and find that it’s well above your target level. If this is a regular occurrence, you may have what’s known as “morning highs.” The term broadly describes a pattern of elevated a.m. blood glucose that occurs frequently enough to be a concern.

The occasional morning high will have little impact on your A1C, a measure of your average blood glucose levels over time that indicates how well managed your diabetes is. But if those highs become consistent, they could push your A1C up into dangerous territory.

“If it happens once in a while, or even once a week, it’s probably not a big factor. But if it’s two, three, four times a week, it’s worth figuring out,” says endocrinologist Robert Gabbay, MD, PhD, chief medical officer at the Joslin Diabetes Center in Boston and a member of the Diabetes Forecast Editorial Board. “The first step is to find out what might be the cause.”

Morning highs can be baffling. After all, you just spent the past nine hours or so sleeping (in other words, not ingesting any carb). What’s going on? Two main culprits prompt morning highs: the dawn phenomenon and waning insulin. A third, much rarer cause, known as the Somogyi effect, may also be to blame.

The Dawn Phenomenon

In the early hours of the morning, hormones, including cortisol and growth hormone, signal the liver to boost the production of glucose, which provides energy that helps you wake up. This triggers beta cells in the pancreas to release insulin in order to keep blood glucose levels in check. But if you have diabetes, you may not make enough insulin or may be too insulin resistant to counter the increase in blood glucose. As a result, your levels may be elevated when you wake up. The dawn phenomenon does not discriminate between types of diabetes. Approximately half of those with either type 1 or type 2 experience it.

Waning Insulin

If your insulin level falls too low overnight, your blood glucose rises. The reasons for the drop in insulin vary from person to person, but it most commonly occurs when your insulin pump settings provide too little basal (background) insulin overnight or if your long-acting insulin dose is too low. Insulin duration—how long the drug works in your body—also comes into play. If you inject your long-acting insulin early, it may not last into the morning.

With the rising cost of insulin, many people are turning to cheaper human insulins, such as NPH. Because of the shorter duration of these insulins, though, morning highs are common. Inject NPH at dinner, for instance, and it may not last until morning, which means you wake up with high glucose. “The fix is to move the NPH injection from dinnertime to bedtime so that it does a better job lasting until the morning,” says Craig Williams, PharmD, a professor of pharmacy at Oregon Health and Science University Medical Center in Portland, Oregon, and an associate editor of Diabetes Forecast. “That’s not too hard if you have NPH and a separate vial of short-acting insulin.” It’s a bit trickier if you’re on an insulin mixture (such as 50/50 or 70/30) because the NPH and short-acting insulin are in a single vial.

The Somogyi Effect

Named after Michael Somogyi, PhD, a chemist who was the first to describe it in the 1930s, the Somogyi effect is the body’s response to low blood glucose (hypoglycemia) during the night. Say you miss dinner or take too much insulin after your evening meal. Your blood glucose may fall too low overnight. Your body
makes more glucose in order to compensate, and you wake up with high blood glucose.

In reality, the Somogyi effect occurs so uncommonly that experts aren’t certain it even exists. “We used to think it was a big deal and spent a lot of time looking for it, but it’s an unusual circumstance,” says Gabbay.

Whether it exists or not, paying attention to nocturnal hypoglycemia should be a priority, says certified diabetes educator Chris Memering, BSN, RN, CDE, FAADE, of CarolinaEast Health System in New Bern, North Carolina. “I still see doctors using the Somogyi effect as a potential reason for a.m. hyperglycemia [high blood glucose], more to help potentially look for nocturnal hypoglycemia, which can be deadly.”

Gather the Clues

If a pattern of frequent morning highs emerges during your routine glucose monitoring, check your blood glucose levels at bedtime, in the middle of the night, and first thing when you wake up to develop a better understanding of your glucose patterns.

“You have to set your alarm and check your blood glucose at 3 a.m. for a week or two,” says Memering. If you use a continuous glucose monitor (CGM), however, you can sleep through the night; it’ll gather the data you need. If you don’t use one, see if your doctor can provide a loaner.

“The CGM is the gold standard,” says Kathleen Dungan, MD, an endocrinologist at The Ohio State University Wexner Medical Center in Columbus, Ohio. The device provides the most precise (and convenient) window into your glucose patterns, revealing glucose levels frequently over long periods of time—without the need for finger sticks.

Identify the Culprit

Your readings will tell you and your doctor when your highs and lows occur and that, in turn, will help narrow the cause of the problem.

  • Data Shows:
    High at bedtime

  • The Culprits:
    Food and medication

If you have high blood glucose before you go to sleep, the elevated level can persist until morning. Gabbay looks at both diet and medication—and their interaction—as possible causes. A large dinner or a snack at bedtime can cause elevated glucose levels that last all night, as can too low a dose of insulin with your evening meal. Adjusting your medication or what and when you eat may help.

  • Data Shows:
    In range at bedtime

  • The Culprit:
    Too little medication

You may go to bed with glucose levels within your target range, but that doesn’t mean they’ll stay that way overnight. “If you are taking a long-acting insulin in the morning and it wears off before the next dose the following day, you would definitely see morning hyperglycemia,” says Dungan.

Changing the timing of your long-acting insulin injection, or switching to a twice-daily basal insulin or an ultra-long-acting insulin, might fix the problem.

Other options exist if you don’t take insulin. Your doctor may first prescribe lifestyle adjustments to help you avoid morning highs, including evening exercise, smaller dinners, and giving up your bedtime snack. Medication changes may enter the mix, too. For example, your doctor may add metformin (if you’re not already taking it), a DPP-4 inhibitor, an SGLT-2 inhibitor, or a GLP-1 receptor agonist.

  • Data Shows:
    High in the wee hours

  • The Culprit:
    The dawn phenomenon

If you’re experiencing the dawn phenomenon, which raises your blood glucose between approximately 3 and 8 a.m., your doctor may recommend that you avoid increasing your long-acting insulin. While a higher dose of insulin will bring your morning highs down to normal, it could cause too great a drop in your blood glucose after you first go to sleep but before your blood glucose starts to rise in the early hours of the morning. “Sometimes the only way to adequately address the dawn phenomenon is with an insulin pump,” says Dungan. You can program the pump to automatically deliver more insulin in the early a.m.

If you don’t use insulin, the dawn phenomenon can be trickier to treat. Most drugs, says Dungan, address both post-meal and fasting blood glucose, while insulin allows a more targeted approach to treating morning highs. As a result, it may take a good bit of trial and error before you and your health care provider figure out the best medication and lifestyle strategy.

You will likely need to make changes to your medications or add new ones. Memering says that your doctor may prescribe a nighttime dose of metformin—or adjust your dose if you already take it. A GLP-1 might also be helpful, she adds. If you eat a bedtime snack to avoid low blood glucose, be sure it contains some protein rather than carbs alone. That way, your body will absorb the snack’s carbs at a steadier rate, which will help prevent a spike in your blood glucose. Eventually, though, you might have to start taking insulin.

Work It Out

Exercise can also help you manage your morning highs. If you have waning insulin, an after-dinner walk or other workout can help keep your blood glucose down overnight, says Memering. But use caution when exercising before bedtime; the glucose-lowering effects of exercise can last for hours, so if you work out before bed, you risk going low overnight.
Morning exercise may be best if your glucose data has shown a trend of nighttime lows after late afternoon or evening exercise. Working up a sweat in the a.m. is a good idea for anyone experiencing the dawn phenomenon, too. “It helps burn up that extra blood glucose,” says Memering.

Try, Try Again

There’s no single recipe to control morning highs. What works for one person may not work for you. It may take time to find the best strategy to keep your blood glucose at the right level in the morning while avoiding hypoglycemia overnight. In rare cases, says Memering, the ideal balance can’t be found. “We’ll change your morning glucose goal so that it’s a little bit higher, as long it stays within goal the rest of the day,” she says. “But for most people, we can figure out what’s happening and what to readjust.”



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