Sweating in your sleep happens when something raises your core body temperature or triggers your sweat glands while your body’s natural cooling system is less responsive. The causes range from a bedroom that’s too warm to medications, hormonal shifts, infections, and occasionally something more serious. Most of the time, night sweats have a straightforward explanation, but persistent drenching sweats deserve attention.
How Your Body Regulates Temperature During Sleep
Your brain actively cools your body as you fall asleep. A region of the hypothalamus detects warmth signals from your skin and responds by widening blood vessels near the surface, letting heat escape. This is why your core temperature drops during the deeper stages of sleep. The cooling isn’t just a side effect of rest; it’s part of what allows deep sleep to happen in the first place. External warmth actually helps initiate deep sleep by triggering this cooling cascade, which is one reason a warm bath before bed can make you drowsy.
During REM sleep (the dreaming stage), your body temporarily loses much of its ability to regulate temperature. Blood vessels constrict, and your brain warms back up. If your environment is too hot during REM, your body can’t compensate the way it does during deeper sleep stages, and sweating kicks in as a backup cooling mechanism. This is why people often wake up sweaty in the second half of the night, when REM periods are longer.
Your Bedroom Is Too Warm
The simplest and most common explanation is environment. Sleep researchers recommend keeping your bedroom between 60 and 65 degrees Fahrenheit (15.5 to 18.3 degrees Celsius). According to UCLA neurologist Alon Avidan, sleeping in a room between 70 and 75 degrees promotes insomnia, and temperatures in that range also increase the likelihood of sweating. Heavy blankets, memory foam mattresses that trap heat, and synthetic sleepwear all compound the problem. Before looking for medical causes, it’s worth ruling out these basics.
Hormonal Changes
Fluctuating estrogen levels are one of the most common medical triggers for night sweats. During perimenopause and menopause, drops in estrogen confuse the hypothalamus into thinking the body is overheating. It responds by dilating blood vessels and activating sweat glands, producing the classic hot flash. Up to 80% of women going through menopause experience these, and they’re often worse at night because the body is already in a state of active temperature regulation.
Night sweats can also occur during other periods of hormonal flux: pregnancy, the menstrual cycle, and in people with low testosterone. The mechanism is similar in each case. The brain’s thermostat becomes more sensitive to small temperature changes and overreacts.
Medications That Cause Night Sweats
Several common medications trigger sweating as a side effect, and many people don’t realize the connection. Antidepressants are among the most frequent culprits. SSRIs like citalopram, escitalopram, fluoxetine, and paroxetine affect serotonin signaling in the hypothalamus and spinal cord, which disrupts normal temperature regulation. The sweating can start within days of beginning the medication or appear weeks later.
Other drug classes linked to excessive sweating include:
- Fever-reducing medications like acetaminophen and ibuprofen, which can cause rebound sweating as they wear off overnight
- Hormone therapies and drugs that block hormone production
- Some diabetes medications, particularly those that can lower blood sugar too aggressively
- Steroids like prednisone
If your night sweats started around the same time as a new prescription, that’s worth mentioning to your doctor. In many cases, adjusting the dose or switching medications resolves the problem.
Low Blood Sugar While You Sleep
For people with diabetes, especially those using insulin, blood sugar can drop dangerously low during the night. When this happens, your body releases a surge of adrenaline to raise blood sugar back up, and that adrenaline activates your sweat glands. The result is waking up with damp sheets and clothing, often feeling confused, tired, or shaky. This can also happen in people without diabetes who skip meals, drink alcohol before bed, or have reactive hypoglycemia. If you regularly wake up sweaty and disoriented, checking your blood sugar levels overnight (with a continuous glucose monitor or a fasting morning test) can help identify the pattern.
Infections and Immune Responses
Your immune system raises your body temperature to fight off infections, and sweating is how your body brings that fever back down. Night sweats that accompany an acute illness like the flu or a cold are straightforward and resolve when the infection clears. But persistent, recurring night sweats without an obvious illness can sometimes point to a chronic infection. Tuberculosis is one of the classic causes, though it’s uncommon in many countries. Bacterial infections of the heart valves (endocarditis), abscesses, and HIV can all produce ongoing night sweats as well.
Anxiety and Stress
Stress activates your sympathetic nervous system, the same fight-or-flight response that releases adrenaline. If you go to bed anxious, or if you experience stress dreams or nightmares, that activation can trigger sweating even when the room is cool. People with anxiety disorders, PTSD, or panic disorder often report night sweats as an ongoing issue. Addressing the underlying anxiety, whether through therapy, lifestyle changes, or medication, tends to reduce the sweating over time.
Alcohol and Spicy Food
Drinking alcohol before bed is a surprisingly common cause of night sweats. Alcohol dilates blood vessels near the skin, increases your heart rate, and stimulates sweat production. It also disrupts sleep architecture, pushing you into lighter sleep stages where temperature regulation is less stable. Even moderate drinking (two or three drinks) can trigger noticeable sweating hours later as your body metabolizes the alcohol. Spicy foods have a similar, though milder, effect by activating heat receptors in the mouth that signal the brain to cool the body down.
When Night Sweats Signal Something Serious
Most night sweats are caused by the factors above and aren’t dangerous. But there’s a meaningful difference between occasionally waking up a little warm and regularly soaking through your sheets. Drenching night sweats, the kind that force you to change your clothes or bedding, are taken more seriously in clinical settings.
Lymphoma and other cancers can cause severe night sweats as one of a cluster of symptoms known as “B symptoms.” These include drenching night sweats, unexplained weight loss (more than 5% of body weight over six to twelve months), and persistent fevers. Swollen lymph nodes in the neck, armpits, or groin that don’t go away after four to six weeks are another red flag, especially when paired with night sweats. Itchy skin, fatigue, and bone pain can also appear alongside these symptoms.
The key distinction is pattern and context. Night sweats that come with unexplained weight loss, fevers, new lumps, or persistent fatigue warrant prompt evaluation. Night sweats that happen after drinking wine in a warm bedroom with a heavy comforter generally don’t.
Thyroid Problems
An overactive thyroid gland raises your basal metabolic rate, meaning your body produces more heat around the clock, including while you sleep. People with hyperthyroidism often experience heat intolerance during the day and sweating at night, along with a rapid heartbeat, weight loss despite increased appetite, and trembling hands. If night sweats are paired with any of these daytime symptoms, a simple blood test can check thyroid function.
Reducing Night Sweats at Home
If you’ve ruled out medical causes, or while you’re working with a doctor to identify one, several changes can reduce how often and how intensely you sweat at night. Keep your bedroom at 65 degrees or below. Switch to breathable bedding made from cotton, linen, or moisture-wicking fabrics, and avoid memory foam pillows that trap heat. Wear lightweight, loose sleepwear or sleep without clothing.
Avoid alcohol, caffeine, and spicy food within three hours of bedtime. If stress is a factor, a wind-down routine that lowers your heart rate before bed (reading, breathing exercises, stretching) can reduce the sympathetic nervous system activation that drives sweating. Keeping a log of when night sweats occur and what you ate, drank, or did that evening can help you spot patterns your doctor can use to narrow down the cause.