Sweating in your sleep is completely normal in most cases. Your body continues regulating its temperature overnight, and sweat is one of its primary tools for doing so. Light perspiration during sleep, especially if your bedroom is warm or you’re bundled under heavy blankets, is a routine physiological response, not a medical concern. That said, there’s a meaningful difference between ordinary nighttime perspiration and what clinicians call “night sweats,” which involve sweating even when your sleep environment isn’t hot.
Why Your Body Sweats During Sleep
Your brain’s temperature control center, located in the hypothalamus, works around the clock. When your core body temperature rises above a narrow comfort zone called the thermoneutral zone, the brain signals sweat glands to activate and cool you down. This system runs on autopilot through your autonomic nervous system, the same network that controls your heart rate and digestion without conscious effort.
The volume and rate of sweat your body produces depends on how much cooling it needs. Thick blankets, a warm room, flannel pajamas, or sleeping next to another person can all raise your skin temperature enough to trigger a perfectly healthy sweat response. Emotional stress and physical exertion earlier in the day can also keep your sweat glands more active into the night.
Normal Sweating vs. True Night Sweats
The clinical distinction is straightforward: if you’re sweating because your bedroom is too warm or your bedding is too heavy, that’s your thermoregulation working as designed. True night sweats happen even when your sleep environment is cool and comfortable. A widely used definition from a 2010 study frames it simply as “sweating at night even when it is not excessively hot in your bedroom.”
True night sweats often soak through your pajamas or sheets and may wake you up. Occasional episodes aren’t necessarily alarming, but if they’re happening regularly, several times a week for more than a few weeks, it’s worth investigating an underlying cause.
Common Causes of Night Sweats
Hormonal Changes
Menopause is the single most common medical cause of night sweats in women. Hot flashes and their nighttime counterpart affect up to 80% of women during menopause, and they persist for an average of 7 to 10 years. The sweating episodes are caused by hormonal shifts that temporarily reset the brain’s thermostat, making it overreact to small temperature changes. Perimenopause, the years leading up to menopause, can trigger the same symptoms. Hormonal fluctuations during pregnancy, menstruation, and puberty can also produce noticeable nighttime sweating.
Medications
Antidepressants are a well-documented trigger. Roughly 10% of people taking SSRIs (the most commonly prescribed type of antidepressant) experience excessive sweating, and the rate climbs to 5 to 20% for SNRIs, another widely used class. Both drug types roughly triple the risk of excessive sweating compared to placebo. If your night sweats started around the same time as a new medication, that connection is worth raising with your prescriber. Other drugs linked to night sweats include hormone therapies, blood pressure medications, and over-the-counter fever reducers as they wear off.
Sleep Apnea
Obstructive sleep apnea, a condition where breathing repeatedly stops and starts during sleep, has a surprisingly strong connection to night sweats. In one study, 31% of people with untreated sleep apnea reported frequent nighttime sweating (three or more times per week), compared to just 11% of the general population. That’s a threefold difference. If your night sweats come with loud snoring, gasping during sleep, or daytime fatigue, sleep apnea could be the underlying issue.
Infections and Illness
Your body raises its core temperature to fight infections, and the sweating that follows is the cooldown phase. This is why you often wake up drenched after a fever breaks. Short-term infections like the flu or COVID cause temporary night sweats that resolve as you recover. Chronic infections, including tuberculosis and certain bacterial infections, can produce persistent drenching sweats over weeks or months.
When Night Sweats Signal Something Serious
Most night sweats trace back to something manageable: a warm bedroom, hormonal shifts, a medication side effect, or a passing illness. But persistent, unexplained night sweats paired with other symptoms deserve medical attention. The combination doctors pay closest attention to is night sweats alongside unexplained weight loss and recurrent fevers. This trio can signal conditions like lymphoma or other blood cancers, chronic infections, or autoimmune diseases. None of these are common causes, but they are the reason persistent night sweats shouldn’t be dismissed indefinitely without evaluation.
There’s no single standardized test for night sweats. Doctors typically start with a detailed history of your symptoms, medications, and overall health, then order bloodwork based on what the pattern suggests. The evaluation is often a process of elimination rather than a single definitive test.
How to Reduce Normal Nighttime Sweating
If your sweating is the garden-variety kind triggered by your sleep environment, a few changes can make a noticeable difference.
Temperature is the biggest lever. Sleep experts at the Cleveland Clinic recommend keeping your bedroom between 60 and 67°F (15 to 19°C). That range feels cooler than most people’s default thermostat setting, but it aligns with your body’s natural temperature drop during sleep. A fan or air conditioning helps, and cracking a window in cooler months can achieve the same effect.
Your bedding matters more than you might expect. Synthetic fabrics like polyester trap heat and moisture against your skin. Natural fibers perform significantly better: cotton, linen, and bamboo-derived fabrics are all breathable and allow airflow to help heat escape. Bamboo and Tencel (made from eucalyptus) are particularly good at wicking moisture away from your body so it evaporates rather than pooling. If you’re choosing cotton sheets, a percale weave is crisper and more breathable than sateen, which tends to feel heavier and hold in warmth. The same principle applies to what you wear to bed: lightweight, natural-fiber sleepwear outperforms synthetic materials.
Beyond bedding, a few habits help. Alcohol and spicy food within a few hours of bedtime can raise your core temperature. Keeping a glass of cold water on your nightstand won’t prevent sweating, but it helps you cool down and rehydrate if you wake up warm. And if you sleep with a partner, consider separate blankets, since shared bedding traps significantly more body heat.