What Causes Night Sweats? A Practical Guide
"Night sweats" technically means sweating heavy enough to soak your sheets and bedclothes — not just warm-bedroom sweating. They're common enough that one large primary-care survey found 41% of adults experienced them in the past month. Most have benign explanations (your bedroom is too warm, you had spicy food, you took a hot shower at night). Some have medical ones that matter. Here's how to tell which is which.
TL;DR
- Cool your bedroom (65-68°F / 18-20°C) and use breathable bedding before assuming a medical cause.
- Most common medical causes: menopause/perimenopause, sleep apnea, certain medications, anxiety.
- Red-flag causes (rare but serious): tuberculosis, lymphoma, HIV, endocarditis, certain cancers.
- See a doctor if night sweats are drenching, recurrent, or paired with weight loss, fever, or fatigue.
Environmental causes (try these first)
Before assuming a medical cause, run the simple test:
- Bedroom temperature. Optimal sleep temperature is 65-68°F (18-20°C). Anything warmer pushes you into compensatory sweating. Use a thermometer; don't trust your morning impression.
- Bedding material. Synthetic sheets and comforters trap heat. Cotton, linen, or specifically "moisture-wicking" bedding work better.
- What you wear to bed. Synthetic pajamas trap heat the same way. Cotton or merino wool sleepwear breathe better.
- Pre-bed habits. Hot showers right before bed raise core temperature for an hour or two. Alcohol causes vasodilation that drives sweating. Spicy food has the same effect via capsaicin.
If you fix all four and still sweat through the sheets, the cause is probably internal.
Common medical causes
Menopause and perimenopause
Hot flashes that occur during sleep cause night sweats. They affect roughly 75% of women in perimenopause, and often start years before menstrual cycles become irregular. They can continue for 7-10 years on average — longer for some.
Treatments include hormone replacement therapy (HRT), certain SSRIs, gabapentin, and lifestyle modifications. A primary care doctor or gynecologist can advise on which fits.
Sleep apnea
Untreated obstructive sleep apnea triples the risk of night sweats. The mechanism: the body's sympathetic nervous system fires up during each apneic episode (when breathing stops), which can drive sweating. Treating the apnea — with CPAP, an oral appliance, or weight loss — often resolves the sweats. If you snore loudly and sweat at night, see our snoring vs. sleep apnea guide.
Medications
Common culprits: SSRIs and SNRIs (antidepressants), tamoxifen and other hormonal cancer therapies, hypoglycemic agents (sometimes), opioids, steroids, niacin at high doses, hormone therapy (sometimes lowers sweat threshold). Don't stop any medication without talking to the prescriber, but flagging "I started this drug and now I'm sweating at night" is useful diagnostic information.
Anxiety and stress
Chronic anxiety raises baseline sympathetic activity, which can manifest as night sweats. People who report panic attacks during sleep often also report drenching sweats. If anxiety is the cause, treating it usually resolves the sweating.
Hyperthyroidism
An overactive thyroid raises metabolic rate and can cause sweating, including at night. Other signs: unintentional weight loss, racing heart, tremor, heat intolerance generally. A simple TSH blood test diagnoses it.
Infections
Tuberculosis is the classic infectious cause — drenching night sweats are a textbook symptom. Endocarditis (heart valve infection), HIV, certain abscesses, and severe respiratory or urinary infections can all cause them. These are less common but more serious.
Hypoglycemia
Low blood sugar at night, especially in diabetics on insulin, can cause sweating. Often accompanied by morning headache or feeling shaky. Worth flagging to your endocrinologist if it's a pattern.
The "B symptoms" that matter
In medicine, "B symptoms" is shorthand for a triad that raises suspicion of serious underlying disease (originally lymphoma, now applied more broadly):
- Drenching night sweats
- Unexplained weight loss (over 10% of body weight in 6 months)
- Persistent fever or fatigue
Any one of these alone is usually benign. The combination of all three warrants prompt medical evaluation. Lymphomas, leukemias, HIV, and tuberculosis are on the differential.
When to see a doctor
- Drenching sweats (have to change clothes or sheets) recurring more than 2-3 times a week
- Sweats plus unintentional weight loss or persistent fatigue
- Sweats plus fever, even low-grade
- Sweats that started after starting a new medication
- Sweats plus loud snoring or witnessed breathing pauses
- Sweats plus any swollen lymph nodes you can feel
Document the pattern
A doctor's first question will be "how often, how heavy, any triggers." SnoreCam's morning highlight reel can surface clips showing you tossing, throwing off covers, or waking briefly — patterns that are otherwise invisible to you. Clips stay on your phone; bring screenshots or descriptions to your appointment.
Related reading
SnoreCam is not a medical device. This article is for informational purposes only and does not constitute medical advice. If you have concerns about your sleep or health, consult a qualified healthcare provider.