Nightly sweating is common and usually caused by something fixable: a warm bedroom, heavy bedding, or a medication side effect. Night sweats are generally defined as sweating during sleep even when your bedroom isn’t excessively hot. While the cause is often straightforward, persistent or drenching night sweats can sometimes signal a hormonal shift, an underlying condition, or rarely something more serious that needs medical attention.
Your Body Temperature Drops at Night
Your brain actively lowers your core body temperature as part of the normal sleep cycle. This cooling process is essential for falling and staying asleep, and your body accomplishes it the same way it cools down during exercise: by dilating blood vessels near the skin and producing sweat. Some degree of perspiration during the night is completely normal physiology.
Problems start when something interferes with this cooling process. If your bedroom is too warm, your bedding traps heat, or your body’s internal thermostat is thrown off by hormones, medications, or illness, the sweating ramps up beyond what’s needed. The result is waking up damp, sometimes soaked, and wondering what’s going on.
A Warm Bedroom Is the Most Common Culprit
The optimal bedroom temperature for sleep is 60 to 67°F (15 to 19°C). Many people sleep in rooms well above this range, especially if they keep heating on overnight or share a bed with a partner. Memory foam mattresses, synthetic sheets, and heavy comforters all trap body heat and make it harder for sweat to evaporate, which amplifies the problem.
Before investigating medical causes, it’s worth running a simple experiment. Lower your thermostat into that 60 to 67°F range, switch to breathable cotton or linen bedding, and sleep in light clothing (or none). If the sweating stops or significantly improves within a few nights, your environment was the issue.
Medications That Cause Night Sweats
If you started sweating at night after beginning a new medication, that’s likely your answer. Antidepressants are among the most common offenders. People taking SSRIs (a widely prescribed class of antidepressants) are roughly three times more likely to report night sweats than people not taking them. The mechanism appears to involve changes in brain chemicals that regulate sweating, specifically increased release of noradrenaline and effects on receptors that control sweat glands.
Other medications frequently linked to night sweats include:
- Fever-reducing drugs like aspirin and acetaminophen, which can trigger rebound sweating as they wear off overnight
- Hormone therapies and drugs that alter hormone levels
- Blood pressure medications
- Some diabetes medications, particularly those that lower blood sugar
If you suspect a medication is responsible, don’t stop taking it on your own. Talk to your prescriber about adjusting the dose or timing, or switching to an alternative.
Hormonal Changes
Fluctuating hormone levels are one of the most frequent medical causes of night sweats. For women in perimenopause and menopause, hot flashes don’t stop at bedtime. The same sudden surges of heat that happen during the day occur at night, triggering intense sweating episodes that can soak through sheets. These episodes are caused by changes in estrogen that affect the brain’s temperature control center, making it overreact to tiny shifts in body heat.
Hormonal night sweats aren’t exclusive to menopause. Men with low testosterone can experience them too, as can people with thyroid conditions. An overactive thyroid speeds up your metabolism and raises your baseline body temperature, making you sweat more around the clock, including during sleep.
Low Blood Sugar During Sleep
If you have diabetes and take insulin or certain glucose-lowering medications, nighttime sweating may be a sign your blood sugar is dropping too low while you sleep. Nocturnal hypoglycemia occurs when blood glucose falls below 70 mg/dL during the night. Your body responds by releasing stress hormones to push glucose back up, and one side effect of that hormonal surge is sweating, along with a racing heart and clammy skin.
This is worth paying attention to because you may not fully wake up during these episodes. Clues include damp sheets in the morning, a headache upon waking, or feeling unusually groggy or irritable when you get up. If this pattern sounds familiar, checking your blood sugar before bed and discussing your medication timing with your doctor can help pinpoint the problem.
Sleep Apnea and Night Sweats
Obstructive sleep apnea, a condition where your airway repeatedly collapses during sleep, is an underrecognized cause of night sweats. The connection makes physiological sense: each time your airway closes, your body mounts a stress response to force you to breathe again, and that stress response triggers sweating. Research from Mayo Clinic found that severe night sweats are linked to intermediate or high risk of sleep apnea, yet 65% of people in that higher-risk group remained undiagnosed two years later.
If your night sweats come alongside loud snoring, gasping during sleep, morning headaches, or daytime exhaustion, sleep apnea is worth investigating. Treating it often resolves the sweating along with the other symptoms.
Infections and Illness
Night sweats can be your body’s way of fighting off an infection. Any illness that causes fever can produce sweating at night as your temperature rises and falls. Common culprits include the flu, COVID-19, sinus infections, and urinary tract infections. In these cases, the sweating resolves once the infection clears.
Chronic or recurring infections can also be responsible. Tuberculosis is historically one of the classic causes of drenching night sweats, though it’s uncommon in many parts of the world today. HIV, endocarditis (an infection of the heart valves), and abscesses can all produce persistent night sweats as well.
When Night Sweats Are a Red Flag
The type of sweating matters. There’s a meaningful difference between waking up a bit damp and experiencing what doctors call “drenching” night sweats, defined as sweating so severe you need to change your bedclothes. Drenching night sweats that persist for weeks, combined with other symptoms, deserve prompt medical evaluation.
The combination that raises the most concern is drenching night sweats plus unexplained weight loss (more than 10% of your body weight over six months) plus unexplained fevers above 100.4°F. This triad is associated with lymphoma and other blood cancers. Easy bruising, persistent fatigue, or swollen lymph nodes that don’t go away after four to six weeks add further reason to get checked.
This doesn’t mean night sweats alone indicate cancer. The vast majority of people with night sweats have a benign cause. But if you’re losing weight without trying, running fevers you can’t explain, or finding enlarged nodes in your neck, armpits, or groin alongside the sweating, those symptoms together warrant blood work and potentially imaging.
What Doctors Look For
When night sweats persist and don’t have an obvious environmental or medication-related explanation, doctors typically start by identifying whether you’re at higher risk for infection or malignancy. They’ll ask about weight changes, fevers, medications, alcohol use, and other symptoms. A physical exam checking for enlarged lymph nodes, thyroid abnormalities, and signs of infection usually comes next.
Blood work can screen for thyroid dysfunction, blood sugar issues, signs of infection, and markers that suggest blood cancers. The specific tests depend on your symptoms and risk factors. For many people, a careful history and basic labs are enough to identify the cause or confirm that nothing worrisome is going on.
Practical Steps to Reduce Night Sweats
While you’re sorting out the underlying cause, a few changes can make nights more comfortable. Keep your bedroom between 60 and 67°F. Use layers of light blankets rather than one heavy comforter so you can adjust easily. Choose moisture-wicking or natural fiber sheets and sleepwear. Avoid alcohol, spicy food, and caffeine in the hours before bed, as all three can raise body temperature or trigger flushing during sleep.
A fan or air conditioning provides airflow that helps sweat evaporate, which is your body’s actual cooling mechanism. Keeping a cold glass of water by the bed won’t prevent sweating, but it helps you recover more comfortably if you wake up overheated. If your sweats are hormonal, some people find that a cool shower before bed helps lower their starting core temperature enough to reduce overnight episodes.