Night sweats can be a sign of hormonal changes, infections, medication side effects, sleep disorders, or occasionally something more serious like lymphoma. The term refers specifically to episodes of sweating severe enough to soak through your sleepwear or sheets, not just feeling warm because your bedroom is stuffy. Most causes are treatable or manageable once identified, but persistent drenching sweats deserve medical attention, especially when paired with unexplained weight loss or fever.
Hormonal Changes Are the Most Common Cause
Fluctuations in estrogen and progesterone directly affect how your brain regulates body temperature. When these hormone levels rise or fall sharply, your internal thermostat can misfire, triggering a wave of sweating to cool you down even though you weren’t overheated. This is why night sweats are so closely tied to perimenopause and menopause. The same mechanism drives hot flashes during the day.
Night sweats from hormonal shifts aren’t limited to menopause. Pregnancy, the postpartum period, and certain phases of the menstrual cycle can all produce them. In men, low testosterone levels can cause similar episodes. Thyroid disorders, particularly an overactive thyroid, ramp up your metabolism and body heat production, leading to sweating around the clock, including at night.
Medications That Trigger Sweating
Antidepressants are one of the most common medication-related causes. Somewhere between 7% and 19% of people taking SSRIs (a widely prescribed class of antidepressants) experience excessive sweating as a side effect, and it often gets worse at night. Other drug categories linked to night sweats include hormone therapies, blood pressure medications, diabetes drugs that can cause low blood sugar overnight, and over-the-counter fever reducers like aspirin or acetaminophen (which work by resetting your temperature, sometimes triggering a sweat response as your body cools).
If your night sweats started around the same time as a new prescription, that timing is worth mentioning to your doctor. The sweating often resolves with a dosage adjustment or a switch to a different medication.
Infections and Immune Responses
Your body raises its temperature to fight infection, and sweating is how it brings that temperature back down. With certain chronic infections, this cycle repeats night after night.
Tuberculosis is one of the classic associations. In its reactivated form, TB typically causes a cough alongside weight loss, low-grade fever, and night sweats that can occur several times per week. HIV infection frequently presents with fever and night sweats, sometimes as early symptoms. Fungal infections like histoplasmosis produce a similar pattern of cough, fever, weight loss, and nocturnal sweating. Even bacterial infections of the heart valves (endocarditis) can cause night sweats through recurring episodes of bacteria entering the bloodstream.
The key pattern with infectious causes is that night sweats rarely appear alone. They almost always come with other symptoms: a persistent cough, ongoing fatigue, fevers, or gradual weight loss.
When Night Sweats Signal Cancer
This is the possibility that drives most people to search, so it’s worth being specific. Night sweats are a recognized symptom of lymphoma, particularly Hodgkin lymphoma, where low-grade fever and drenching night sweats are the most common systemic symptoms. In some patients, night sweats are the only initial complaint. Non-Hodgkin lymphoma can also cause them, though less frequently.
The sweats associated with lymphoma tend to be severe, soaking through clothing and bedding rather than just making you damp. They also persist over weeks. Doctors look for a specific cluster of warning signs: unintentional weight loss greater than 5% of your body weight over six to twelve months, persistent fevers, and swollen lymph nodes. Nodes that have been swollen for more than four to six weeks alongside night sweats raise concern for malignancy and typically prompt a biopsy without delay.
That said, lymphoma is far less common than the hormonal, medication, or lifestyle causes on this list. Occasional night sweats without other symptoms are very unlikely to indicate cancer.
Sleep Apnea and Night Sweats
About 30% of people with obstructive sleep apnea report night sweats, and the rate is notably higher than in the general population (roughly 19% of sleep apnea patients versus 12% of people without it in one study). The connection involves your body’s stress response. When your airway closes repeatedly during sleep, each awakening and the physical effort of resuming breathing spike your sympathetic nervous system, the same system that controls your fight-or-flight response. That surge increases sweating.
If your night sweats come with loud snoring, gasping during sleep, or persistent daytime fatigue, sleep apnea is worth investigating. Treating the underlying breathing problem often resolves the sweating.
Acid Reflux as an Overlooked Cause
Gastroesophageal reflux disease (GERD) is increasingly recognized as a potential trigger for night sweats. The relationship isn’t as well established as hormonal or infectious causes, but researchers have noted the association frequently enough that reflux deserves consideration during a diagnostic workup for unexplained night sweats, particularly when someone also has heartburn, chest discomfort, or a sour taste at night.
Rare Endocrine Causes
A pheochromocytoma is a tumor on the adrenal gland that pumps out adrenaline and noradrenaline at inappropriate times, essentially triggering your fight-or-flight response when there’s no actual threat. Heavy sweating is one of the hallmark symptoms, alongside sudden spikes in blood pressure, rapid heartbeat, and headaches. These episodes come and go in distinct “spells” rather than being constant. This condition is rare, but its pattern of sudden, intense sweating attacks with heart pounding and anxiety is distinctive.
Lifestyle and Environmental Triggers
Before assuming a medical cause, it’s worth ruling out the simple stuff. Alcohol before bed is a common trigger, as it dilates blood vessels and disrupts temperature regulation as your body metabolizes it. Spicy foods, caffeine consumed later in the day, and smoking can all provoke nighttime sweating in susceptible people.
Your sleep environment matters more than you might think. Fleece, flannel, down comforters, and synthetic fiber sheets trap heat against your body. Switching to lightweight bedding makes a measurable difference. For sleepwear, synthetic moisture-wicking fabrics (typically polyester blends) pull sweat away from your skin and allow it to evaporate significantly faster than cotton, which absorbs moisture and holds it against you. Keeping your bedroom cool and using a fan can also reduce the frequency and severity of episodes.
Patterns That Warrant a Medical Visit
Isolated episodes of waking up sweaty, especially after drinking alcohol, sleeping under heavy blankets, or during a brief illness, are normal and not cause for concern. The pattern that doctors take seriously is persistent, drenching night sweats occurring regularly over weeks. Combine that with any of the following and the evaluation becomes more urgent: unintentional weight loss, fevers that you can confirm with a thermometer, swollen lymph nodes that don’t go away, a persistent cough, or significant fatigue.
A typical evaluation starts with blood work and a thorough physical exam including a check of all your lymph node groups. Depending on what that reveals, imaging or further testing may follow. In many cases, the cause turns out to be something straightforward like a medication side effect or hormonal shift, and targeted treatment brings relief relatively quickly.