Sleep hyperhidrosis: why do I sweat at night even when it's not warm?

2026 07 07

You wake up drenched despite the bedroom being cool. The bedding is damp, your top is soaked — and this is not the first time. If night sweats recur regularly and do not seem to be related to temperature, this is a signal worth understanding rather than ignoring.

What is sleep hyperhidrosis?

Hyperhidrosis is the medical term for excessive sweating that cannot be explained by ambient temperature or physical activity. Nocturnal hyperhidrosis (or simply "night sweats") is one of the most common problems that disrupts sleep quality — and it has specific causes that can be identified and often — resolved.

8 real reasons why you sweat at night

1. Bedding that is too warm or the wrong fabric

This is the most common and most easily resolved cause. Microfibre, flannel or thick-fabric bedding traps body heat close to the skin and does not allow it to dissipate. Even if the bedroom is cool, a microclimate builds up under the duvet where the body becomes too warm.

Synthetic fabrics are particularly problematic — they do not allow moisture or air through, so sweat remains on the skin instead of evaporating.

Solution: choose breathable bedding — percale, Tencel or linen. These fabrics actively regulate moisture and body temperature rather than accumulating it.

2. Hormonal changes

Night sweats are one of the clearest symptoms of hormonal imbalance. This is particularly relevant for:

Women during menopause — fluctuations in oestrogen levels directly affect the thermoregulation centre in the brain and cause hot flushes that often occur at night
During pregnancy — increased blood volume and hormonal changes cause increased sweating
Men over 40 — declining testosterone levels can cause symptoms similar to female menopause

If night sweats began alongside other hormonal symptoms — it is worth consulting a doctor.

3. Stress and anxiety disorders

Night sweats are often not a physical but a psychological problem. Stress activates the sympathetic nervous system — the "fight or flight" response — and this causes sweating even during sleep.

People with generalised anxiety disorder, post-traumatic stress disorder or chronic stress frequently report regular night sweats as one of their symptoms. The brain does not sleep as deeply as it should — and the body responds accordingly.

4. Certain medications

Night sweats are a known side effect of many medications:

Antidepressants (particularly the SSRI group — fluoxetine, sertraline, escitalopram)
Diabetes medications (nocturnal hypoglycaemia causes sweating)
Hormonal preparations
Some antibiotics
Fever-reducing medications (can paradoxically trigger a rebound reaction)

If night sweats began after starting new medications — inform your doctor. Often a dose adjustment or medication change is sufficient.

5. Infections and chronic conditions

Night sweats are a classic symptom of certain health conditions:

Tuberculosis — historically, night sweats were one of its main symptoms
HIV/AIDS — night sweats can be a sign of early infection
Chronic bacterial infections — endocarditis, osteomyelitis
Brucellosis — symptom of a rare bacterial infection
Fungal infections — some systemic mycoses

If night sweats are accompanied by fever, weight loss or general weakness — this is a serious signal to see a doctor.

6. Oncological conditions

Although it is a rare cause, night sweats combined with weight loss and enlarged lymph nodes can be a symptom of lymphoma or other cancers. This is not mentioned to cause alarm — but it is one of the reasons why regular, unexplained night sweats are not a trivial matter to be ignored.

7. Hypoglycaemia (low blood sugar)

The night is the longest break between meals — and in some people, particularly those with diabetes or taking insulin, blood sugar can drop during the night. The body responds by releasing adrenaline, which causes sweating, palpitations and restless sleep.

If you wake up feeling weak, dizzy or hungry — these may be signs of nocturnal hypoglycaemia.

8. Thyroid overactivity (hyperthyroidism)

An overactive thyroid accelerates metabolism and raises body temperature — classically causing increased sweating both day and night. Other symptoms: rapid heart rate, weight loss, anxiety, hair loss.

When to see a doctor

Night sweats are not always a medical problem — but there are situations where consultation is necessary:

The sweating is so intense that you need to change bedding or clothing during the night
It lasts longer than a few weeks without a clear cause
It is accompanied by fever, weight loss, fatigue or enlarged lymph nodes
It began alongside new medications
It disrupts sleep so much that you feel exhausted during the day

What you can do today

1. Change your bedding
This is the quickest solution if the cause is the temperature of the fabric. Breathable natural fabrics — percale, Tencel, linen — actively regulate moisture and prevent heat from building up. All three options are available in Savashome's bedding category.

2. Lower the bedroom temperature
The ideal bedroom temperature — 16–19 °C. Many people keep their room too warm and wonder why they sweat even under thin bedding.

3. Sleep in light clothing or without
Synthetic sleepwear (polyester, nylon) traps heat in the same way as synthetic bedding. Choose cotton or linen.

4. Avoid alcohol and spicy food in the evening
Both of these factors dilate blood vessels and raise body temperature — often causing night sweats even in people who do not normally have this problem.

5. Review your medications
If you take any regular medications — check whether night sweats are a side effect. This can be found in the package insert or discussed with your doctor.

6. Get checked
If the problem does not disappear after changing the bedding and bedroom temperature — consult a doctor for blood tests: thyroid hormones (TSH, T3, T4), blood sugar, ferritin and a full blood count.

In summary

Night sweats are not merely an inconvenience. They are a signal the body is sending, and they can mean very different things: from bedding that is too warm to a hormonal imbalance or a more serious health condition.

Start with the simplest — bedding, temperature, medications. If that does not help — do not sweep the problem under the carpet but consult a doctor. Night sweats are a solvable problem — you just need to find the right cause.