How A Good Night’s Sleep Helps Your Blood Sugar Levels

This is what happens to your blood sugar levels when you sleep—here's how to improve your sleep quality and quantity for better health

Regularly getting a good night’s sleep is important if you want to generally be awake, productive, and not cranky. Sleeping well at night helps us all to be functional. But it’s also key in keeping our hormones in check and helping us avoid metabolic diseases, like type 2 diabetes.

In fact, research shows a link between poor sleep and type 2 diabetes. “Overall, the literature suggests people with sleep disorders have a 25-30 percent higher risk of developing prediabetes or type 2 diabetes,” says Robert H. Eckel, MD, professor of medicine emeritus in the division of endocrinology, metabolism, and diabetes at the University of Colorado Anschutz Medical Campus, and president of medicine and science at the American Diabetes Association.

“Association does not necessarily mean cause and effect, so we have to be careful there,” he cautions. There’s also plenty of research showing a connection between poor sleep and weight gain—which can then, in turn, increase someone’s risk of developing type 2 diabetes over time. Be sure to avoid these 9 diabetes myths.

The connections here are complex and not completely clear, but one thing is: Sleeping a sufficient amount (the National Sleep Foundation recommends seven to nine hours for adults) each night is a good habit that can help your body maintain healthy blood sugar levels.

Understanding blood sugar and insulin

Insulin is an essential hormone that’s produced in the pancreas. Insulin’s main job is to take glucose from our bloodstream (which comes from the food we eat) and use it to power cells throughout the body, according to the Endocrine Society. When it does its job properly, our cells get the energy they need without our blood sugar levels soaring too high or dropping too low.

People with type 2 diabetes either don’t produce enough insulin or have developed insulin resistance, according to the Centers for Disease Control and Prevention. When someone develops insulin resistance, that means their cells don’t respond to insulin the way they should, causing glucose to build up in the blood and blood sugar levels to skyrocket.

Blood sugar levels drop slightly during sleep

Overnight, blood glucose levels fall modestly and settle into a normal fasting level, and insulin levels tend to be lower because there’s no stimulus prompting its release, Dr. Eckel says. “In people with type 2 diabetes, glucose levels are probably maintained at a higher level overnight depending on how they manage the condition,” he adds. (This may differ if, for example, someone takes medication to control their type 2 diabetes vs using diet and lifestyle modifications.) Try these 15 diabetic foods your body will enjoy.

blood sugar and diabetes and sleepMarkHatfield/Getty ImagesBlood sugar levels may go haywire with lack of sleep

Even for people without type 2 diabetes, sleep deprivation changes how effective insulin is at its job, says Dr. Eckel. In 2016, a small study of 15 young non-obese adults, published in the journal Sleep Health, showed that restricting sleep for just one to three hours for three days caused signs of reduced insulin sensitivity (meaning the body became more resistant to it) compared to three nights where the participants could sleep as long as they wanted. Similar studies on how partial sleep deprivation impacts insulin sensitivity and blood glucose levels have shown similar findings.

Studies like this show that “insulin resistance occurs in normal people with just a few nights of sleep deprivation,” says Dr. Eckel. “That same insulin resistance has been well documented in people with type 2 diabetes who have altered sleep patterns.”

The effectiveness of insulin may also be impacted by the way sleep deprivation messes with our natural production of other hormones, namely growth hormone and the stress hormone, cortisol. “Several hormones are released while we sleep, and a perfect balance of these is necessary for optimal energy, immunity, and appetite,” says Salma Batool-Anwar, MD, MPH, an instructor at Harvard Medical School and pulmonary, critical care, and sleep medicine physician at Brigham and Women’s Hospital in Boston.

A few nights of poor sleep every now and then isn’t worth stressing over, though.

While it only takes a few nights of suboptimal sleep to impact the way our bodies process sugar, it’s not like doing this every so often is going to cause long-term issues or directly lead to type 2 diabetes. A bad night of sleep once in a while won’t wreak havoc, says Dr. Eckel. Just like nutrition or exercise, it’s about being consistent most of the time, but you don’t have to be “perfect” to be generally healthy.

If your sleep deprivation is persistent and long-lasting, the impact would be greater, he says. Even still, poor sleep is just one factor that can impact your risk of type 2 diabetes. “Type 2 diabetes doesn’t just show up because of sleep disturbance. It plays on top of things like inactivity, poor diet, being overweight, and family history. There are many other factors that play a role,” says Dr. Eckel. If you’re feeling sleep-deprived, try these 8 tips to stay sharp.

Lack of sleep may disrupt hunger hormones

Another factor in the web of connections between sleep, weight, and type 2 diabetes risk is how poor sleep can disrupt hunger hormones in the body and lead to overeating.

Sleep is important for maintaining hormones that control our appetite—leptin and ghrelin, says Dr. Batool-Anwar. “Leptin signals a sense of fullness, so when we have high levels, appetite is blunted. Ghrelin signals hunger, so when we have high ghrelin, we have a strong sensation of hunger. Inadequate sleep decreases leptin and increases ghrelin,” she explains. That’s why you want to snack when you’re exhausted. And sleep-deprived people aren’t typically reaching for fruits and veggies. “Research has supported that sleep-deprived individuals take in more carb-rich foods and salty foods,” says Dr. Batool-Anwar. “So sleep deprivation is a perfect recipe for gaining weight.” A higher body weight, in turn, increases the risk of developing type 2 diabetes.

It can keep you from exercising and thus, disrupt blood sugar levels

“When sleep deprived, you wake up tired and tend to have a more sedentary lifestyle,” says Dr. Batool-Anwar. Not only does physical inactivity reduce the number of calories you burn, but if you’re not exercising, you’ll miss out on the ways it can benefit blood sugar. One bout of exercise can lower blood sugar in the short-term (for about 24 hours after) because it increases insulin sensitivity and makes your muscle cells better able to use insulin and take in glucose for energy, according to the American Diabetes Association. Your muscles can even take in glucose during exercise, whether enough insulin is available to help or not.

Regular exercise can lower average blood glucose, a marker called A1C, according to the government health information site Medline Plus. A1C is used to test for diabetes and determine how well you’re managing the disease. This is why exercise is so beneficial for managing type 2 diabetes in the long term.

Type 2 diabetes can disrupt sleep

There’s a little bit of a chicken-or-the-egg situation here that’s important to mention: Yes, poor sleep impacts blood sugar, and chronic sleep deprivation can increase your risk of developing type 2 diabetes. But also, type 2 diabetes can increase your risk of sleep deprivation.

“People with type 2 diabetes have more sleep disturbances and obstructive sleep apnea,” says Dr. Eckel. A large number of people with type 2 diabetes are overweight or obese, which is strongly associated with sleep apnea. There could also be an independent factor that leads people with type 2 diabetes to sleep poorly, but Dr. Eckel says it’s likely a result of being overweight or obese.

Focus on both sleep quantity and quality

Sleeping the recommended seven to nine hours per night is a good place to start. But just because you’re in bed and feel like you’re sleeping, it doesn’t mean you’re getting the deep, restorative sleep you need. Deep sleep may be the most important when it comes to letting hormones like cortisol and growth hormone fluctuate properly, according to the National Sleep Foundation.

If you feel exhausted despite clocking sufficient hours in bed, you may have a problem with sleep quality. Of course, if you have a bed partner, they can tell you if you snore or kick a ton in your sleep. If you don’t, talk to your doctor about how you feel so they can help you figure out where your sleep debt is coming from and how you can get more restful sleep each night. Plus, learn what your sleep habits are trying to tell you.

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Amy Marturana Winderl
Amy is a freelance journalist and certified personal trainer. She covers health and fitness, outdoors, travel, and finance. Her work has appeared on SELF, Bicycling, Earnest, and other publications. When she's not busy writing or editing, you can find her hiking, cooking, running, or lounging on the couch watching the latest true crime show on Netflix.