There are many unanswered questions in life, but “Why do I sweat in my sleep?” shouldn’t be one of them. A night spent tossing and turning, waking up to damp sheets, pajamas that stick to you—all signs you might be a hot sleeper. But why? There are a lot of factors that could be at play here, according to experts. If you are waking up early because of your night sweats, it might be a cause that’s easy to fix, like too-warm pajamas. But if you’re experiencing hot flashes at night regardless of what you wear to bed, it could be time to talk to your doctor.
“When you sweat while you’re sleeping, your body is losing water while it should actually be in a state to conserve fluids, since you don’t have any fluid intake at night,” explains sleep scientist Roy Raymann, PhD, chief scientific officer at SleepScore Labs. “While some minimal perspiration is normal at night, sweating that can be easily noticed or even wake you up from sleep might need some special attention.” You may have sleep hyperhidrosis—excessive night sweating, in medical terms.
Although it may seem easy to dismiss a few pit stains here and there, Michael Breus, PhD, a sleep specialist and author of Good Night: The Sleep Doctor’s 4-Week Program to Better Sleep and Better Health, says that cold sweats while sleeping is nothing to joke around with.
“Night sweats can also be signs of other medical issues, including infection, adrenal dysfunction, and cancer,” Breus says. “With such a broad range of possible causes for night sweating, it’s important to speak with your physician if you observe any changes to the typical ways your body sweats at night—if you begin to sweat more frequently, or if your sweating increases in intensity.”
While “why do I sweat so much in my sleep” may not be the sexiest Google search, there are solutions available. Not only is there advice at your fingertips with the help of sleep apps that track your cycle, but there are also common mistakes to avoid to ensure a good night’s rest.
Below, we asked the experts to answer some common questions about what causes night sweats and how to solve them. You’ll never have to ask yourself “Why do I sweat in my sleep?” again.
Is it healthy to sweat while sleeping?
If your night sweats are infrequent, don’t sweat it. (Pun intended.) “It’s normal to occasionally sweat while sleeping,” says Shelby Harris, PsyD, director of sleep health at Sleepopolis. However, she says, frequent night sweats that wake you up in the middle of the night can be a sign of other medical conditions.
When should I be worried about night sweats?
According to Dr. Harris, your night sweats might be a red flag if they’re accompanied by other symptoms like a high fever or weight loss or routinely interfering with your sleep three or more nights a week. If so, she advises talking to your doctor or a sleep specialist.
Can dehydration cause night sweats?
Not necessarily. “Sweating is a completely natural function of your body,” says Dr. Harris. “Your body constantly works to make sure your core temperature doesn’t exceed approximately 98° Fahrenheit. Hydration is extremely important for maintaining your body temperature, and it may affect the intensity of your night sweats. If you’re dehydrated before you go to bed, you’ll most likely sweat less but you will feel overheated. However, if you’re well-hydrated, you will likely sweat more as your body tries to cool down.”
So why do I sweat so much in my sleep, even if I’m in a cold room?
“Bedding and sleepwear are the most common reasons people sweat in their sleep,” says Dr. Harris. “Even if the bedroom temperature is cold, sleeping in materials that aren’t breathable and don’t promote airflow can cause overheating and night sweats.”