What Happens to Your Body When You Don't Get Enough Sleep?

person sleeping in bed with white bedding

Getty / Luis Alvarez

We’ve all been there before: You promise yourself just a few more minutes—and suddenly, it’s 2 a.m. and you’re still wide awake. Perhaps you’re binging a new favorite Netflix series or fretting over a morning meeting— whatever the root cause, you’re tossing and turning in bed all night, instead of getting the shut-eye you so desperately need. What most of us don’t understand, however, is what really happens to our bodies when we don’t achieve that optimal level of sleep, which for most adults clocks in between seven and eight hours. Ahead, we asked a few doctors to explain how are bodies react to too-little sleep—and their answers might surprise you.

Related: How to Combat Short-Term Insomnia for a Better Night’s Sleep

It becomes more difficult to focus on mental and physical tasks.

According to Dr. Jan K. Carney, MD, MPH, the Associate Dean for Public Health & Health Policy, and Professor of Medicine at Larner College of Medicine at the University of Vermont and the National Institutes of Health, sleep is essential for health at every age. “When we don’t get enough sleep, it is harder to stay alert, focus on school or work, and react quickly when driving,” Dr. Carney says.

Your memory and mood suffers—and your appetite increases.

Sleep physician Dr. Abhinav Singh, MD, FAASM, the Medical Director of the Indiana Sleep Center, and Sleep Foundation Medical Review Panel member, says that, believe it or not, losing precious hours of sleep and drinking excessive amounts of alcohol have similar physical consequences. “Sleep loss is linked to memory impairment, poor mood, increased appetite (think obesity and diabetes), and reduced reflexes,” he says. “Increased reaction time and some studies have compared it to being worse than being intoxicated with alcohol.”

Long-term sleep shortage could lead to chronic physical and mental health concerns.

While Dr. Carney says the short-term risks of sleep loss are things we’re all familiar with—feeling drowsy and having trouble concentrating—the real risk is what a compounded lack of sleep can do over time. “Longer-term sleep shortage is associated with increased risks for chronic health conditions such as high blood pressure, heart disease, obesity, stroke, and depression.”

You can’t make up for lost sleep.

Unfortunately, you can’t “catch up” on sleep—once those hours are gone, they’re gone for good. “It is best to develop and keep regular sleep habits over the long term,” shares Dr. Carney, adding that you also can’t “learn to live” with less sleep. “The best way to ensure both adequate sleep and high-quality sleep is to develop good sleep habits.” This means implementing a routine with a consistent bedtime and wake time each day—even on weekends. “Regular exercise helps, as does avoiding caffeine or alcohol near bedtime,” Carney says. “Our environment is essential—we need a calm, quiet, dark, and cool location where we sleep regularly.”