If your blood sugar levels are elevated when you wake up in the morning, you may be experiencing what’s known as the dawn phenomenon. It’s a common scenario: High morning blood sugar occurs in more than half of people with type 1 diabetes and type 2 diabetes.

Those who successfully manage the dawn phenomenon typically employ a mix of strategies to help get their blood glucose better under control, including adjusting medication, dietary changes, exercising more, and other lifestyle tweaks.

High morning blood sugar happens when your body secretes a surge of hormones, including growth hormone, epinephrine, and cortisol, typically between 3 a.m. and 8 a.m. These hormones directly cause an increase in blood sugar. This is a normal part of waking up, but in people with diabetes, this temporary rise in blood sugar is more powerful and longer lasting than it should be.

“Those hormones affect insulin sensitivity and can increase blood glucose levels if you don’t adjust your insulin doses,” says Ben Tzeel, RD, CDCES, founder of Your Diabetes Insider. If someone uses insulin to manage their diabetes, Tzeel says, they may need to adjust their dosage in the morning to account for this effect.

Experts say the dawn phenomenon is not the only cause of high blood sugar readings in the morning.

What you eat in the evening matters, too. “If you tend to eat late at night, right before bed, or you're eating very high-fat or high-protein meals at dinner, that could spike your blood sugar in the second half of the night,” says Tzeel.

Meals with plenty of protein and fat tend to result in a delayed blood sugar rise — one that might occur after you’ve fallen asleep. If you take insulin before meals, it’s possible that you went to bed without realizing that you would need more insulin to keep your blood sugar in range.

High blood sugar in the morning can also be a sign of diabetes progression and increasing insulin resistance, which is when the body’s cells don’t respond properly to insulin. If your fasting blood glucose is increasing over time, you may need to intensify your diabetes treatment, possibly by taking new medication or larger doses of the medication that you already use, such as long-acting insulin.

A final possible explanation is the Somogyi effect, which is also known as rebound hyperglycemia. This happens when low blood sugar (hypoglycemia) in the middle of the night triggers your liver to release stored glucose in larger amounts than usual. It’s unclear how often the Somogyi effect actually occurs. “I haven’t personally seen the Somogyi effect much in practice, and I think it’s very rare,” says Lauren Graf, RD, CDCES, a diabetes specialist and a nutritionist for the Montefiore Health System.

The easiest way to understand your overnight blood sugars is to use a continuous glucose monitor (CGM). This device, which measures and records your blood sugar around the clock, will show you the entire night’s worth of blood sugar values, making it easy to identify which direction your blood sugar moved while you slept.

“If you go to bed with in-range blood glucose levels, and your CGM says you’re pretty steady through most of the night, but your blood glucose starts spiking noticeably around 3 a.m., it’s likely the dawn phenomenon,” says Tzeel.

If you don’t use a CGM, it’s not as easy to see your overnight blood sugar trends. But you can test your blood sugar levels multiple times, including in the middle of the night, for a few days in a row.

If you understand the pattern of your overnight blood sugar changes, it’s easier for you and your clinician to determine the cause and address the problem.

There are several strategies you can try to combat the effects of the dawn phenomenon.

If you use rapid-acting insulin every day, the best solution may be switching to an insulin pump. These devices allow you to program different dosage settings for different times of day. Insulin pump users can administer more insulin during the morning hours, when the dawn phenomenon takes place.

“With support from your diabetes care team, you’d want to increase your basal rate about one hour before the spike in your blood glucose typically starts, because it takes an hour for that basal insulin to really kick in,” says Tzeel.

Insulin pumps with automated insulin delivery (AID) make such adjustments automatically, changing your insulin dosage in real time in response to the dawn phenomenon and other blood sugar variables.

Other options to prevent or treat the dawn phenomenon include:

Avoid carbohydrates at bedtime, as they may cause overnight blood sugar spikes.
Troubleshoot the delayed blood sugar rise from meals with lots of fat or protein.
Exercise in the evening to enhance your insulin sensitivity overnight.
Start the day with an exercise session, which can help lower your blood sugar level quickly.
Adjust the time when you take your glucose-lowering medication or insulin.

It’s possible to begin the day with a dose of rapid insulin to help combat the “feet on the floor” effect. Graf, however, says managing the dawn phenomenon with insulin injections can be a little more challenging because you can’t control exactly when the insulin will peak. “You can work with your healthcare team to shift the timing of your long-acting insulin or split the dose to help it hit based on when the long-acting peaks,” says Graf. “Getting the dose and the timing as accurate as possible isn’t easy and will probably take a lot of patient experimenting.”

The Takeaway

The dawn phenomenon is a common cause of elevated morning blood sugar levels due to hormonal surges overnight that trigger glucose release.
Blood sugar levels can also rise overnight due to your eating and lifestyle habits, including late-night snacking or dinners with lots of fat or protein. Using a continuous glucose monitor is the best way to help you identify the problem.
High morning blood sugar levels may also be a sign that you are experiencing an increase in insulin resistance.
Sharing your overnight blood sugar trends with your medical team is the best way to collaborate on a solution, which may require a change in your diet, lifestyle habits, or use of diabetes medication.

Menu

The Takeaway