Night sweats are episodes of heavy sweating during sleep that aren’t caused by an overly warm bedroom or too many blankets. They’re surprisingly common, and the causes range from hormonal shifts and medications to sleep disorders and, less often, serious underlying conditions. Understanding what’s behind them can help you figure out whether yours are a nuisance or a signal worth investigating.
What Counts as Night Sweats
Not every sweaty night qualifies. The working clinical definition is sweating at night even when your bedroom isn’t excessively hot. True night sweats are distinct from simply feeling warm because you overdressed for bed or left the heat running. People who experience them often describe waking up with damp or soaked sheets, sometimes needing to change clothes or bedding before going back to sleep. They can happen once in a while or multiple times a week, and the pattern and severity offer clues about the cause.
Hormonal Changes
The most common trigger for night sweats, especially in women, is shifting levels of estrogen and progesterone. These hormones help regulate your body’s internal thermostat. When their levels rise or fall sharply, the brain’s temperature-control center can misread your actual body temperature, deciding you’re overheating when you’re not. The response: a sudden wave of heat followed by heavy sweating as your body tries to cool itself down.
This is why night sweats are so closely linked to perimenopause and menopause, when hormone levels fluctuate most dramatically. Low estrogen in particular is a well-established cause. But hormonal night sweats aren’t exclusive to menopause. They also show up during pregnancy, the menstrual cycle, and in people receiving hormone therapy or hormone-blocking treatments for conditions like prostate cancer or breast cancer.
Medications That Trigger Sweating
Several widely prescribed drugs list excessive sweating as a side effect, and the sweating often shows up most noticeably at night when you’re lying still and aware of it. The biggest culprits include:
- Antidepressants: SSRIs (like citalopram and sertraline) and older tricyclic antidepressants are frequent offenders. If your night sweats started shortly after beginning or adjusting an antidepressant, the timing is probably not a coincidence.
- Pain medications: Opioid painkillers and even some over-the-counter anti-inflammatory drugs can cause sweating.
- Hormone-related medications: Corticosteroids, thyroid medications, and diabetes drugs can all disrupt the body’s temperature regulation.
- Antipsychotics: Drugs used for psychiatric conditions are another recognized cause.
If you suspect a medication is behind your night sweats, it’s worth raising the question with your prescriber. Sometimes a dose adjustment or switch to a different drug in the same class resolves the problem.
Overactive Thyroid
Your thyroid gland produces hormones that influence how every cell in your body uses energy, and they play a direct role in controlling body temperature and heart rate. When the thyroid is overactive, a condition called hyperthyroidism, it floods your bloodstream with too much of these hormones. The result is a body running hotter and faster than it should be.
People with hyperthyroidism often notice increased sensitivity to heat, a rapid or pounding heartbeat, and sweating that worsens at night. Sleep problems are common too, which can make the sweating feel even more disruptive. Other signs include unexplained weight loss, anxiety, and trembling hands. If night sweats come packaged with several of these symptoms, thyroid function is worth checking.
Sleep Apnea
About 30% of people with obstructive sleep apnea report night sweats. The connection isn’t always obvious, but the physiology makes sense. During apnea episodes, your airway repeatedly collapses, cutting off oxygen. Each time your brain jolts you awake (often without you fully realizing it), there’s a spike in sympathetic nervous system activity, the same fight-or-flight response that makes you sweat during stress. Over the course of a night with dozens or hundreds of these micro-awakenings, the cumulative effect can leave your sheets soaked.
The telltale signs of sleep apnea alongside night sweats include loud snoring, gasping during sleep (often noticed by a partner), morning headaches, and feeling exhausted despite what seemed like a full night of rest. Treating the apnea, usually with a device that keeps the airway open during sleep, often resolves the sweating as well.
Infections
Night sweats are a classic feature of certain infections. Tuberculosis is the textbook example, producing drenching sweats night after night, but bacterial infections of the heart valves (endocarditis), bone infections, and abscesses can do the same. HIV can also cause persistent night sweats, particularly when the infection is undiagnosed or untreated. Even common viral and bacterial illnesses can cause temporary sweating at night as your body fights off the infection and runs a fever.
The distinction here is pattern. A few nights of sweating during a cold or flu is normal. Weeks of unexplained, drenching sweats that persist after any acute illness has passed deserve attention.
Lymphoma and Other Cancers
This is the cause people worry about most, and while it’s far less common than hormonal shifts or medication effects, it’s real. Night sweats are one of the hallmark symptoms of lymphoma, both Hodgkin and non-Hodgkin types. The sweats associated with lymphoma tend to be drenching, the kind that soak through your pajamas and sheets, and they recur regularly.
Importantly, lymphoma-related night sweats rarely appear in isolation. They typically come alongside other symptoms: swollen lymph nodes (often in the neck, armpits, or groin), unexplained weight loss, persistent fatigue, fevers, and sometimes chills. If your night sweats are accompanied by any combination of these, especially unexplained weight loss or painless swelling of lymph nodes, that constellation of symptoms warrants prompt evaluation. Other cancers, including leukemia and certain solid tumors, can also cause night sweats, though less characteristically than lymphoma.
Other Common Causes
Several additional triggers are worth knowing about because they’re easy to overlook or address:
Anxiety and stress. Chronic stress keeps your sympathetic nervous system on high alert, and that heightened state doesn’t always switch off at bedtime. People with anxiety disorders or high baseline stress often report sweating during sleep, sometimes alongside vivid dreams or restless sleep.
Alcohol. Drinking before bed dilates blood vessels and disrupts your body’s temperature regulation during the night. Even moderate amounts can cause noticeable sweating, and the effect is more pronounced with heavier consumption.
Low blood sugar. People taking insulin or certain diabetes medications can experience drops in blood sugar overnight. The body responds with a surge of adrenaline, which triggers sweating. If you manage diabetes and wake up sweating, checking your blood sugar at the time of the episode can help confirm or rule this out.
Idiopathic hyperhidrosis. Some people simply produce excessive sweat without any identifiable medical cause. This can happen during the day, at night, or both. It tends to run in families and isn’t dangerous, though it can be disruptive.
When Night Sweats Signal Something Serious
Most night sweats have an identifiable, manageable cause. But certain patterns raise the stakes. Pay attention if your night sweats are persistent (lasting more than a few weeks), drenching rather than mild dampness, and accompanied by unexplained weight loss, fevers, swollen lymph nodes, or persistent fatigue. These combinations are what clinicians look for when deciding whether to investigate more aggressively with blood work or imaging.
A single episode after a spicy meal or a warm night is nothing to worry about. Recurring, soaking sweats that disrupt your sleep and don’t have an obvious explanation, like a new medication or a hot bedroom, are worth bringing up at your next appointment. The cause is usually something treatable, and identifying it is the first step toward sleeping dry again.