Waking up soaked in sweat is surprisingly common, and in most cases the cause is something straightforward: your bedroom was too warm, you had alcohol before bed, or your body’s natural temperature cycle dipped a little too aggressively. But when it happens repeatedly or comes with other symptoms, it can signal something worth investigating, from medication side effects to hormonal shifts to, rarely, a more serious underlying condition.
How Your Body Controls Temperature During Sleep
Your core body temperature starts dropping about two hours before you fall asleep, part of a natural circadian rhythm that cues your brain it’s time for rest. During deep sleep, your temperature drops further, sometimes by a full degree Celsius over the course of the night. This cooling process is active, not passive. Your brain’s thermoregulatory center triggers blood vessel dilation in your skin and, when needed, sweating to push heat out of your body.
Normally this process is subtle enough that you sleep through it. But if anything disrupts the system, whether it’s an overly warm room, extra blankets, a fever, or a hormonal shift, your brain can overcorrect. The result is the kind of drenching sweat that wakes you up with damp sheets and a racing heart.
The Most Likely Culprits
Your Sleep Environment
The simplest explanation is often the right one. Sleep research points to a room temperature of roughly 19 to 21°C (66 to 70°F) as optimal, because your body tries to maintain a skin temperature between 31 and 35°C while you sleep. Heavy comforters, memory foam mattresses that trap heat, synthetic pajamas, or a room above that range can all push your body past its comfort threshold and trigger heavy sweating. If you woke up soaked once and it doesn’t keep happening, your bedding or thermostat is the first thing to check.
Alcohol
Drinking in the evening is one of the most common triggers for night sweats. Alcohol widens blood vessels in your skin (vasodilation), which makes you feel flushed and warm. Your heart rate increases. Your skin releases sweat to compensate. Because most people drink in the hours before bed, the peak of this effect often lands squarely during sleep. People with alcohol use disorder may also experience night sweats as a withdrawal symptom, as the nervous system rebounds after the sedative effects wear off.
Medications
Antidepressants are a well-known cause. Excessive sweating affects an estimated 4 to 22 percent of people taking SSRIs or SNRIs, and it often shows up at night. Other common offenders include fever reducers (which can cause rebound sweating as they wear off), hormone therapies, and some blood pressure medications. If your night sweats started around the same time as a new prescription, that connection is worth exploring with your prescriber.
Hormonal Changes and Menopause
For people going through perimenopause or menopause, night sweats are one of the most disruptive symptoms. The mechanism is well understood: as estrogen levels decline, a group of neurons in the brain becomes hyperactive and essentially lowers the trigger point for your body’s heat-release response. Normally, your brain tolerates small fluctuations in core temperature without reacting. With lower estrogen, that tolerance window narrows, so even a tiny, normal rise in body temperature during sleep can set off a full heat-dissipation response: flushing, vasodilation, and drenching sweat.
These episodes can last anywhere from a few seconds to several minutes, and for some people they happen multiple times per night. They’re not dangerous, but they significantly disrupt sleep quality and can persist for years.
Sleep Apnea
This one catches many people off guard. Obstructive sleep apnea, where your airway repeatedly collapses during sleep, is strongly associated with night sweats. In one large Icelandic study, about 31 percent of men and 33 percent of women with sleep apnea reported sweating at least three times per week, compared to roughly 9 to 12 percent of the general population. The sweating likely results from the stress response your body mounts each time breathing is interrupted. If you also snore heavily, wake up with headaches, or feel exhausted despite a full night’s sleep, sleep apnea is worth considering.
Infections and Fever
Any infection that causes a fever can produce night sweats. Your immune system often ramps up its inflammatory response during sleep, which is why fevers tend to spike at night. As the fever breaks, your body sweats heavily to cool down. This is the classic “fever broke overnight” experience, and it’s usually temporary. Common culprits include the flu, COVID, sinus infections, and urinary tract infections.
Chronic infections like tuberculosis are a well-known cause of persistent, drenching night sweats, though this is far less common in countries with lower TB prevalence. The sweats in these cases tend to recur nightly and are often accompanied by a persistent cough, fatigue, and unintentional weight loss.
Low Blood Sugar
People with diabetes, particularly those on insulin, can experience night sweats when blood sugar drops below 70 mg/dL during sleep. This is called nocturnal hypoglycemia. Your body responds to dangerously low blood sugar by flooding your system with stress hormones, which trigger sweating, a rapid heartbeat, and sometimes trembling. You might also notice clammy skin, restless sleep, or morning headaches. If you manage diabetes and wake up sweating regularly, checking your overnight blood sugar patterns can reveal whether this is the cause.
When Night Sweats Signal Something Serious
Rarely, persistent night sweats are an early sign of lymphoma or another blood cancer. The pattern that raises concern is specific: drenching sweats that soak through your clothes and bedding, happening repeatedly over weeks, combined with other “B symptoms.” Those B symptoms include unexplained weight loss of more than 10 percent of your body weight over six months and recurring fevers without an obvious infection. Swollen lymph nodes, particularly in the neck or above the collarbone, are another red flag.
To be clear, the vast majority of night sweats have a benign cause. An isolated episode, or even occasional sweating without other symptoms, is not a reason to worry about cancer. The concern arises when the sweats are persistent, severe, and accompanied by the specific combination of symptoms described above. NHS clinical guidelines note that if night sweats are your only symptom and your blood work is normal, further investigation typically isn’t needed.
Practical Steps to Reduce Night Sweats
Start with your environment. Keep your bedroom between 19 and 21°C. Switch to breathable, moisture-wicking bedding and sleepwear. Avoid alcohol within a few hours of bedtime, since even moderate drinking can trigger overnight sweating in some people.
If you’re taking an antidepressant or other medication that may be contributing, don’t stop it on your own, but do raise the issue at your next appointment. Dose adjustments or switching to a different medication in the same class can sometimes resolve the problem. For menopausal night sweats, hormonal and non-hormonal treatment options exist that can significantly reduce the frequency and intensity of episodes.
Track your episodes for a couple of weeks. Note what you ate and drank, the room temperature, your bedding, any medications, and whether you had other symptoms. That pattern often reveals the trigger faster than any test would.