Night sweats have dozens of possible causes, ranging from a too-warm bedroom to hormonal shifts, medications, infections, and occasionally something more serious like lymphoma. True night sweats are repeated episodes of heavy sweating during sleep, enough to soak through your pajamas or sheets. If you’re just feeling a little damp because your room is warm or you piled on too many blankets, that’s not the same thing and usually isn’t a sign of a medical problem.
The distinction matters because true, recurring night sweats often point to something happening inside your body that deserves attention. Here’s a breakdown of the most common reasons.
Hormonal Changes and Menopause
Declining estrogen is the single most common medical cause of night sweats. During perimenopause and menopause, fluctuating estrogen levels disrupt the brain’s temperature control center in the hypothalamus. Normally, this cluster of brain cells keeps your internal thermostat within a comfortable range. When estrogen drops, that thermostat becomes hypersensitive and misreads small temperature changes as overheating. Your body launches a cooling response: blood vessels near the skin dilate to release heat (causing flushing), and your sweat glands kick into overdrive.
This is the same mechanism behind daytime hot flashes, but during sleep you experience it as drenching sweats. These episodes can begin years before your last period and persist well into postmenopause. Hormone-related night sweats tend to come in waves, often multiple times per night, and many people notice they cluster around the upper body, neck, and face.
Hormonal night sweats aren’t exclusive to menopause. Thyroid disorders, particularly an overactive thyroid, can raise your baseline metabolic rate and trigger sweating around the clock. Low testosterone in men can produce a similar pattern of nighttime flushing and sweating.
Medications That Cause Night Sweats
Antidepressants are one of the most frequently overlooked culprits. In a primary care study, people taking SSRIs were about three times more likely to report night sweats than those not on the medication, with roughly 1 in 5 users affected. The sweating likely happens because these drugs interfere with certain receptors that regulate blood vessel tone and trigger the release of noradrenaline, a chemical that activates sweat glands.
SSRIs aren’t the only medications involved. Other common offenders include:
- Other antidepressants (especially SNRIs and tricyclics)
- Hormone therapies (tamoxifen, aromatase inhibitors, GnRH agonists)
- Blood sugar medications (insulin and some oral diabetes drugs, where night sweats signal a low blood sugar episode)
- Fever reducers (aspirin, acetaminophen, ibuprofen, which can paradoxically cause rebound sweating)
- Steroids (prednisone and similar corticosteroids)
If your night sweats started or worsened shortly after beginning a new medication, the timing is a strong clue. In many cases, switching to a different drug in the same class resolves the problem.
Infections
Night sweats paired with fever, unexplained weight loss, or a persistent cough can signal an active infection. Tuberculosis is one of the classic associations. In its most common pulmonary form, TB typically causes cough alongside constitutional symptoms like weight loss, low-grade fever, and night sweats several times per week.
HIV infection frequently presents with fever and night sweats, sometimes as the first noticeable symptoms. As the immune system weakens, secondary infections can layer on additional sweating. Fungal infections like histoplasmosis and coccidioidomycosis produce a similar pattern of cough, fever, and night sweats that can look a lot like TB.
Even more common infections can be responsible. Infectious mononucleosis, caused by the Epstein-Barr virus, produces night sweats significantly more often than other upper respiratory infections, particularly during the acute phase of illness. Infectious endocarditis, an infection of the heart valves, causes sweats related to waves of bacteria entering the bloodstream during sleep. These episodes are usually accompanied by other symptoms like fatigue, chills, and malaise.
Sleep Apnea
This is a surprisingly common and underrecognized cause. About 31% of people with obstructive sleep apnea report frequent nighttime sweating (three or more times per week), compared to roughly 11% of the general population. When your airway collapses repeatedly during sleep, your body mounts a stress response each time, releasing adrenaline and activating your sympathetic nervous system. That fight-or-flight activation drives up your heart rate and triggers sweating.
If your night sweats come with loud snoring, gasping awake, daytime sleepiness, or morning headaches, sleep apnea is worth investigating. Treating the underlying breathing problem, typically with a CPAP device, often resolves the sweating.
Lymphoma and Other Cancers
Night sweats are one of the “B symptoms” used to stage lymphoma, alongside unexplained fever and weight loss of more than 10% of body weight over six months. The defining feature of cancer-related night sweats is their intensity: they’re drenching, the kind that forces you to change your bedclothes. They tend to recur consistently rather than happening once or twice.
Lymphoma is the cancer most strongly linked to night sweats, but other malignancies can cause them too, including leukemia and certain solid tumors. The sweating is thought to result from the immune system’s inflammatory response to the cancer, releasing signaling molecules that reset the body’s thermostat much like an infection does.
To be clear, cancer is a relatively rare cause of night sweats compared to hormones, medications, and infections. But persistent, drenching sweats that come with other unexplained symptoms like weight loss, swollen lymph nodes, or fatigue warrant a medical evaluation.
Alcohol and Other Lifestyle Triggers
Drinking alcohol, even in moderate amounts, can trigger night sweats through a straightforward mechanism. Alcohol speeds up your heart rate and causes blood vessels in the skin to widen. That dilation pulls heat from your core to the surface, making your skin feel flushed and warm, which triggers your sweat glands. The irony is that while you feel hot, your core temperature is actually dropping as heat escapes through the dilated vessels.
Heavy or chronic drinking amplifies this effect, and alcohol withdrawal produces even more severe sweating as the nervous system rebounds into a hyperactive state. Spicy foods work through a similar pathway: capsaicin activates heat receptors in your mouth and gut, and your brain responds as if your body temperature has risen, launching a cooling response that includes flushing and sweating.
Caffeine consumed too close to bedtime, intense evening exercise, and high-sugar meals before sleep can all contribute. These causes are usually easy to identify through the timing pattern.
What Doctors Look For
When night sweats persist without an obvious explanation, the standard medical workup starts with blood tests and imaging. A typical initial panel includes a complete blood count (to check for signs of infection or blood cancers), a tuberculosis screening test, thyroid hormone levels, an HIV test, a C-reactive protein level (a general marker of inflammation), and a chest X-ray. The goal is to rule out the serious causes efficiently before exploring less common possibilities.
Your doctor will also ask detailed questions about timing, severity, accompanying symptoms, medications, and family history. A single episode of waking up sweaty after a night of drinking is very different from weeks of drenching sweats with unexplained weight loss, and the workup reflects that difference.
Practical Steps to Reduce Night Sweats
Regardless of the underlying cause, keeping your sleep environment cool helps. Sleep experts at the Cleveland Clinic recommend a bedroom temperature between 60 and 67°F (15 to 19°C). Anything above 70°F is considered too warm for quality sleep. Moisture-wicking sheets and lightweight, breathable sleepwear can reduce the discomfort of episodes even if they don’t prevent them entirely.
Beyond temperature, limiting alcohol, spicy foods, and caffeine in the hours before bed reduces the likelihood of triggering an episode. If you suspect a medication is responsible, keep a log of when the sweats started relative to any prescription changes. That information helps your doctor make a faster connection. For hormone-related sweats, several treatment options exist that your doctor can tailor to your symptoms and medical history.