Why Do I Sweat at Night drops logoWhy Do I Sweat at Night?

Night sweats, sorted by situation · Updated October 2026

Why Do I Sweat at Night? Causes by Situation

Answer: it depends on when it happens. In a warm bed, it's usually just heat. In a cold room, around your period, after having a baby, when you're sick or on a new medicine, the cause is usually inside your body. Find your situation below, then check the red flags.
Man sitting on the edge of his bed at night wondering why he sweats in his sleepShop now: Good Sleep cooling & heating topper →

Almost everyone sweats a little in their sleep; it's how your body sheds heat. What brings people to this page is the more annoying version: waking up damp or soaked, changing your shirt at 3 a.m., or flipping the pillow to find a dry side. The fastest way to work out why is to think about when it happens.

Find your situation

When the room or bed is warm

The simplest case: your body is shedding heat. Warm rooms, memory foam, flannel sheets and heavy comforters all slow heat loss.

Try: Bedroom around 60–67°F, breathable bedding, and a cooler sleep surface.

When you're cold

Sweating in a cold room usually means the heat is coming from inside: hormones, alcohol, medication, a fever breaking, or the wrong mix of heavy covers in a chilly room.

Try: Read our guide to sweating at night when you're cold.

Around your period, in perimenopause or menopause

Hormone shifts change how your brain controls temperature. The days before a period, perimenopause and menopause are classic times for night sweats. If you're in your late 30s to early 50s and this is new, this guide to perimenopause night sweats covers that stage in depth.

Try: Track it against your cycle and talk to your doctor if it disrupts sleep.

After having a baby

Estrogen and progesterone drop sharply after birth and your body clears extra fluid from pregnancy, so heavy night sweats in the first weeks are common, according to Cleveland Clinic.

Try: See our postpartum night sweats guide for how long they last.

When you're sick

Fever raises your temperature set point; when it breaks, you sweat to cool down. Infections are a common short-term cause of night sweats.

Try: Rest, fluids, and see a doctor for a high or lasting fever.

On a new medication

Mayo Clinic lists some antidepressants, hormone treatments, diabetes medications and fever reducers among drugs that can cause night sweats.

Try: Ask your prescriber; don't stop a medication on your own.

After drinking

Alcohol widens blood vessels in the skin and disrupts sleep later in the night.

Try: Finish drinks about three hours before bed.

When you're stressed or anxious

Stress hormones raise heart rate and turn on sweat glands, sometimes with nightmares.

Try: Wind-down routine, and talk to your doctor if anxiety is affecting sleep.

Woman checking her temperature with a thermometer, sweating at night when sick
A fever breaking is one of the most common short-term causes of a sweaty night.

Less common medical causes

Mayo Clinic and MedlinePlus also list overactive thyroid, low blood sugar, sleep apnea, acid reflux, infections such as tuberculosis, and some cancers such as lymphoma. These usually come with other symptoms, which is why the red-flag list below matters. When no cause is found, doctors may call it idiopathic hyperhidrosis.

Fixes that help in every situation

Good Sleep has a solid rundown of night sweats causes and solutions on its blog, and if you're replacing sheets, start with this list of the best bedding for night sweats.

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When to see a doctor

These are drawn from Mayo Clinic, Cleveland Clinic and MedlinePlus guidance.

Common questions

Why do I sweat at night when I sleep?Most often because your room, mattress or bedding is too warm. Other common reasons are hormones (periods, pregnancy, postpartum, perimenopause and menopause), alcohol, medication, stress and infections. Less often, conditions such as an overactive thyroid, low blood sugar, sleep apnea or some cancers are involved.
Why do I sweat at night when I'm cold?Because the trigger is internal. Hormone shifts, alcohol, medication and fevers can all make you sweat in a cold room. Sweating then makes you feel colder as it evaporates.
Why do I sweat at night so much?Heavy sweating that soaks your clothes or sheets is what doctors call night sweats. If it happens often in a cool room, keep a log and see a doctor, especially if you also have fever, weight loss or a cough.
Why do I sweat at night on my period?Estrogen drops in the days before and during a period, which can affect the brain's temperature control. After ovulation, progesterone also raises body temperature slightly.
How long do postpartum night sweats last?Cleveland Clinic says postpartum night sweats are usually worst in the first couple of weeks and typically settle within about six weeks, though breastfeeding can prolong them.
Why do I sweat at night when sick?A fever resets your internal thermostat higher. When it comes back down, your body sweats to cool off, often at night.
What's the best bedding for night sweats?Breathable, quick-drying fabrics such as cotton percale, linen or moisture-wicking blends, a light blanket instead of a heavy duvet, and a mattress surface that doesn't hold heat.
When are night sweats serious?When they're frequent, soak the bed in a cool room, or come with fever, unexplained weight loss, a persistent cough, swollen glands or pain. Then see a doctor.

Guides

Sources

  1. Mayo Clinic: Night sweats, causes
  2. MedlinePlus (NIH): Night sweats
  3. Cleveland Clinic: Night sweats
  4. Cleveland Clinic: Postpartum night sweats
  5. Cleveland Clinic: Progesterone
  6. Cleveland Clinic: Fever
  7. Cleveland Clinic: The ideal sleeping temperature for your bedroom

By the Good Sleep team · Not medical advice