Waking up soaked in sweat is surprisingly common. In a study of over 2,200 primary care patients, 41% reported experiencing night sweats within the past month. Most of the time, the cause is something fixable: your bedroom is too warm, a medication is interfering with your body’s temperature regulation, or a hormonal shift is narrowing the range of temperatures your body can tolerate without triggering a sweat response. Occasionally, though, persistent drenching sweats signal something that needs medical attention.
Your Bedroom May Be the Simplest Explanation
Before looking at medical causes, it’s worth ruling out the obvious. The ideal sleeping temperature is between 65 and 68°F (15.6 to 20°C). Anything above that range, especially combined with heavy bedding or synthetic fabrics that trap heat, can push your body into active cooling mode while you sleep. Your core temperature naturally dips at night as part of your sleep cycle, and when your environment fights that process, sweating is the result.
Memory foam mattresses, polyester sheets, and thick duvets are frequent culprits. Switching to moisture-wicking fabrics and keeping your thermostat in that 65 to 68°F range is the cheapest experiment you can run. If you’re still waking up drenched after making those changes, something physiological is likely going on.
Medications That Cause Night Sweats
A wide range of common medications list excessive sweating as a side effect, and many people don’t make the connection. The most frequent offenders include:
- Antidepressants (SSRIs and SNRIs): Medications like citalopram, escitalopram, fluoxetine, paroxetine, and venlafaxine affect serotonin signaling in the part of your brain that controls body temperature.
- Tricyclic antidepressants: Older antidepressants like amitriptyline and imipramine stimulate receptors in the peripheral nervous system that ramp up sweating.
- Opioid pain medications: Codeine, morphine, oxycodone, tramadol, and fentanyl trigger a chain reaction involving histamine release that leads to sweating.
- Steroids: Prednisone, dexamethasone, and hydrocortisone influence the hormones that regulate body temperature.
- Thyroid medications: Levothyroxine, if dosed too high, essentially mimics an overactive thyroid, one hallmark of which is excessive sweating.
If your night sweats started or worsened around the time you began a new medication, or changed a dose, that connection is worth raising with whoever prescribed it. In many cases, adjusting the dose or switching to a different drug in the same class resolves the problem.
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: estrogen helps regulate a zone of core body temperatures your brain considers “normal.” When estrogen drops, that zone narrows dramatically. A tiny increase in core temperature that your body would previously have ignored now triggers a full heat-dissipation response, with flushing, rapid heart rate, and profuse sweating.
This isn’t just discomfort. It’s an exaggerated, rapid heat-dump response driven by changes in brain chemistry. Declining estrogen also alters norepinephrine activity in the brain, which further destabilizes temperature regulation. In clinical studies, estrogen therapy significantly raised the temperature threshold at which sweating kicks in, reducing the frequency of hot flashes and night sweats. That said, hormone therapy isn’t the only option, and the severity of symptoms varies enormously from person to person.
Night sweats from hormonal changes can also occur during pregnancy, the menstrual cycle, and with low testosterone levels.
Sleep Apnea: A Frequently Missed Connection
One of the most underrecognized causes of night sweats is obstructive sleep apnea. In an Icelandic study comparing people with sleep apnea to the general population, about one-third of adults with sleep apnea reported frequent night sweats (three or more times per week), a rate three times higher than people without the condition. The pattern held for both men and women.
Sleep apnea causes your airway to repeatedly collapse during sleep, leading to drops in blood oxygen and brief arousals. Each of those events activates your sympathetic nervous system, the same “fight or flight” response that causes sweating during stress. If you also snore heavily, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea is a strong possibility. Treating it, typically with a CPAP machine, often resolves the sweating along with the other symptoms.
Low Blood Sugar During Sleep
People with diabetes, particularly those taking insulin or certain oral medications, can experience nocturnal hypoglycemia, where blood sugar drops below 70 mg/dL during the night. When this happens, the body releases stress hormones to mobilize stored glucose, and one of the side effects is hot, clammy, sweaty skin. You might also wake up with a headache, feeling shaky, or with your heart racing.
This is more common than many people realize, partly because mild episodes can happen without fully waking you up. You just find damp sheets in the morning. If you’re on blood sugar-lowering medication, checking your glucose when you wake up sweaty can help identify the pattern.
Infections and the Immune System
Chronic infections are a classic cause of night sweats, and the reason they happen specifically at night is tied to your body’s circadian rhythm. Cortisol, a hormone that suppresses the immune response and keeps fever in check, naturally drops to its lowest levels during the nighttime hours. With less cortisol circulating, your immune system ramps up its activity, fever spikes, and the subsequent cooling phase produces sweating.
Tuberculosis is the textbook example. Night sweats are one of its hallmark symptoms, alongside prolonged cough, weight loss, and fatigue. Bacterial endocarditis (an infection of the heart valves), HIV, and certain fungal infections can also produce persistent night sweats through this same fever-and-cool-down cycle. These infections tend to develop slowly and produce nonspecific symptoms, which is why they can go undiagnosed for weeks or months.
When Night Sweats Could Signal Cancer
This is the possibility most people are worried about when they search this question. Night sweats are one of the “B symptoms” used to stage Hodgkin lymphoma and some non-Hodgkin lymphomas. The clinical definition is specific: drenching sweats that soak through your bedclothes and require you to change your sheets or pajamas. The sweats from lymphoma are typically persistent, occurring repeatedly over weeks, and they usually come alongside unexplained weight loss (more than 10% of body weight) and recurring fevers.
Cancer-related night sweats are relatively rare compared to all the other causes on this list. But the combination of drenching sweats, unintentional weight loss, and persistent fatigue is the pattern that warrants prompt evaluation.
Figuring Out the Cause
Because night sweats have so many possible triggers, the process of figuring out yours typically starts with a detailed history: when the sweats started, how severe they are, what medications you take, and whether you have other symptoms like weight changes, fatigue, or fever. If nothing obvious emerges from that conversation, a standard workup usually includes blood counts, thyroid function testing, inflammatory markers, tuberculosis screening, HIV testing, and a chest X-ray.
A few patterns can help you narrow things down before that appointment. Sweats that started with a new medication point to drug-induced causes. Sweats accompanied by snoring and daytime exhaustion suggest sleep apnea. Sweats that coincide with missed periods or irregular cycles in your 40s or 50s point toward perimenopause. And sweats that come with weight loss, fevers, or swollen lymph nodes need urgent attention. Tracking when the sweats happen, how severe they are, and what else you notice can give your provider a much clearer starting point.