Persistent sweating, respiratory symptoms and medical investigation
Unravelling the Mystery of Night Sweats: Causes, Tests, and Management
Night sweats are episodes of excessive sweating during sleep that soak nightclothes or bedding despite a comfortably cool room. Although they are often related to menopause, medicines, anxiety or environmental heat, persistent episodes can sometimes accompany infection, obstructive sleep apnoea, hormonal disorders or other illnesses requiring assessment.
- Common causes
- Respiratory infections
- Sleep apnoea
- Hormonal changes
- Diagnostic tests
- Management
Most cases are not caused by cancer
Menopause, anxiety, medicines, low blood sugar, alcohol and environmental overheating are more common explanations.
Consider the complete symptom pattern
Fever, persistent cough, weight loss, swollen glands, haemoptysis, loud snoring or witnessed breathing pauses can guide further investigation.
What are night sweats?
Sweating is one of the body’s normal temperature-control mechanisms. It is therefore common to perspire when the bedroom is warm, the bedding is heavy or a fever is resolving.
Clinically significant night sweats are different. They are often described as drenching, may require a change of clothing or bedding and can repeatedly interrupt sleep.
Normal night-time sweating
Mild perspiration caused by a warm bedroom, thick duvet, synthetic sleepwear or exercise close to bedtime.
Hot flushes
Sudden waves of heat, flushing and sweating that may occur during the day or night, particularly around menopause.
Drenching night sweats
Recurrent soaking episodes in a cool environment, particularly when associated with other symptoms.
Keep a brief symptom record
Record how often the sweating occurs, whether clothes or bedding must be changed, the bedroom temperature, medicines taken and associated symptoms. This can make the clinical assessment more precise.
When should you be concerned about night sweats?
An isolated episode during a warm night is rarely concerning. Medical review becomes more appropriate when sweating is recurrent, unexplained, severe or associated with other symptoms.
Arrange a medical review when:
- episodes occur regularly;
- clothing or bedding becomes soaked;
- sleep is repeatedly disrupted;
- there is no clear environmental explanation;
- symptoms continue for several weeks;
- a new medicine may be contributing;
- the episodes are worrying you.
Additional warning symptoms include:
- unexplained weight loss;
- persistent fever or chills;
- a cough lasting more than three weeks;
- coughing up blood;
- persistent or enlarged lymph nodes;
- significant breathlessness;
- marked fatigue or weakness;
- persistent diarrhoea or pain.
Seek urgent help for severe associated symptoms
Seek urgent medical advice for coughing up blood, rapidly worsening breathlessness, severe chest pain, fainting, confusion, or a very high temperature with marked deterioration. Call 999 for severe or life-threatening symptoms.
What causes night sweats?
Menopause
Changes in temperature regulation can produce hot flushes and drenching night sweats.
Medicines
Antidepressants, corticosteroids, painkillers and some hormone treatments may increase sweating.
Anxiety
Autonomic arousal, nightmares and panic symptoms can trigger sweating and disturbed sleep.
Low blood sugar
Nocturnal hypoglycaemia can cause sweating, tremor, vivid dreams or waking with a headache.
Alcohol or drugs
Alcohol, recreational drugs and withdrawal states can disturb temperature regulation.
Infection
Fever caused by a respiratory or systemic infection may produce sweating as body temperature changes.
Obstructive sleep apnoea
Repeated airway obstruction and arousal can be associated with nocturnal sweating, particularly when snoring, gasping or daytime sleepiness is also present.
Hyperhidrosis
Some people sweat excessively without an identifiable underlying disease.
Hormonal and metabolic causes of night sweats
Perimenopause and menopause
Changing oestrogen levels affect the hypothalamus, which helps regulate temperature. Hot flushes may cause sudden heat, flushing, palpitations and sweating.
Pregnancy and the postnatal period
Hormonal shifts and changes in blood flow and fluid balance can increase sweating. Fever or feeling unwell still requires assessment.
Low testosterone
Testosterone deficiency can cause hot flushes, although the diagnosis requires an appropriate clinical and biochemical assessment.
Hyperthyroidism
Excess thyroid hormone can cause heat intolerance, sweating, tremor, palpitations and weight loss.
Hypoglycaemia
Low glucose triggers adrenaline release, potentially causing sweating, palpitations, shaking and disturbed sleep.
Phaeochromocytoma
This rare catecholamine-producing tumour may cause episodic sweating, headaches, palpitations and high blood pressure.
Hormonal treatment requires an individual assessment
Hormone replacement therapy may improve menopausal symptoms, but it is not suitable for everyone. Treatment should consider symptoms, medical history, preferences and potential benefits and risks.
Medicines that can cause night sweats
Medicines can alter neurotransmitters, hormone levels, blood glucose, pain responses or central temperature regulation. Sweating that starts after treatment is introduced or its dose is changed may suggest a connection.
| Medicine group | How it may contribute | Important action |
|---|---|---|
| Antidepressants | SSRIs, SNRIs and some other antidepressants can alter central temperature regulation | Discuss persistent sweating with the prescriber; do not stop suddenly |
| Glucose-lowering medicines | Insulin and some tablets can cause nocturnal hypoglycaemia | Check glucose as advised and seek review for repeated episodes |
| Hormone-blocking treatment | Reduced oestrogen or testosterone activity can cause hot flushes and sweating | Discuss symptom control with the prescribing specialist |
| Opioids | Opioids can affect autonomic and temperature regulation | Review dose, interactions and withdrawal risk with the prescriber |
| Corticosteroids | Steroids can disturb sleep, glucose and temperature regulation | Do not stop long-term steroids abruptly |
| Alcohol or drug withdrawal | Autonomic overactivity can cause sweating, tremor, agitation and disturbed sleep | Severe withdrawal can be dangerous and requires medical help |
Never stop prescribed medication without advice
Sudden withdrawal from antidepressants, corticosteroids, opioids, sedatives or other medicines can cause harm. A clinician can determine whether a dose adjustment, timing change or alternative medicine is appropriate.
Why infections can cause night sweats
Infection activates inflammatory signals that may raise the body’s temperature target and produce fever. Sweating commonly occurs when that target subsequently falls and the body releases heat.
Infection activates immunity
Immune cells release inflammatory signals in response to a virus, bacterium, fungus or parasite.
Temperature rises
The hypothalamus increases the temperature set point, causing chills and fever.
The set point falls
As fever resolves naturally or after treatment, the body now feels too warm.
Sweating releases heat
Blood vessels dilate and perspiration increases to cool the body.
Tuberculosis
TB can cause persistent cough, fever, night sweats, reduced appetite, fatigue and unexplained weight loss.
Endocarditis
Infection of the heart lining or valves may cause persistent fever, sweating, fatigue, breathlessness or weight loss.
HIV and opportunistic infection
Acute HIV or infections associated with immune suppression can produce fever and drenching sweating.
Bone or joint infection
Osteomyelitis or deep infection may cause persistent pain, fever, fatigue and night sweats.
Kidney infection
Pyelonephritis can cause fever, sweating, flank pain, urinary symptoms and nausea.
Travel-related infection
Malaria and other imported infections should be considered after relevant travel, particularly when fever recurs.
Respiratory causes of night sweats
Tuberculosis
TB is an important consideration when night sweats occur with a persistent cough, fever, weight loss or blood-stained sputum.
Pneumonia
Pneumonia may cause cough, fever, sputum, breathlessness, pleuritic chest pain and sweating as temperature fluctuates.
Lung abscess
A collection of infection within the lung can cause prolonged fever, sweating, weight loss and offensive sputum.
Bronchiectasis exacerbation
Worsening infection may cause increased cough, sputum, fever, fatigue and night-time sweating.
Fungal lung infection
Chronic pulmonary aspergillosis and some endemic fungal infections can cause cough, haemoptysis, weight loss and systemic symptoms.
Respiratory viruses
Influenza, COVID-19 and other viral illnesses can produce fever, sweating, cough and fatigue.
Persistent respiratory symptoms can be assessed through the London Chest Specialist chest infection diagnosis and treatment service .
Night sweats do not identify a specific infection
Diagnosis depends on the wider symptom pattern, examination, exposure history, travel, imaging and targeted microbiological or laboratory testing.
Obstructive sleep apnoea and night sweats
OSA causes repeated narrowing or closure of the upper airway during sleep. These episodes can produce oxygen changes, increased breathing effort and brief arousals that activate the sympathetic nervous system.
Loud habitual snoring
Regular loud snoring is common in OSA, although snoring alone does not confirm the diagnosis.
Witnessed breathing pauses
A partner may notice pauses followed by gasping, choking, snorting or abrupt breaths.
Unrefreshing sleep
Repeated arousals may leave a person tired despite apparently sleeping for an adequate number of hours.
Daytime sleepiness
Falling asleep unintentionally, impaired concentration or sleepiness while driving requires prompt assessment.
Morning symptoms
Morning headache, dry mouth or a sore throat may accompany sleep-disordered breathing.
Cardiometabolic risk
OSA is more common with obesity, resistant hypertension, type 2 diabetes, atrial fibrillation and several other conditions.
Night sweating cannot diagnose sleep apnoea
The association is supportive rather than diagnostic. Clinical assessment and an appropriate sleep study are needed to confirm or exclude OSA.
Read more in the guide to obstructive sleep apnoea and snoring .
Other possible causes of night sweats
Anxiety and panic
Sympathetic nervous-system activation can produce palpitations, rapid breathing and sweating.
Gastro-oesophageal reflux
Reflux may disturb sleep and has been reported alongside night sweating, although persistent symptoms should not automatically be attributed to reflux.
Autoimmune inflammation
Vasculitis, rheumatoid disease and other inflammatory conditions can cause fever, sweating, pain and fatigue.
Neurological disorders
Damage to autonomic pathways can impair sweating and temperature regulation.
Idiopathic hyperhidrosis
Excessive sweating can occur without a detectable infection, endocrine disorder or other underlying disease.
No identified cause
Investigation does not always identify a single explanation, particularly when no warning features are present.
Do night sweats mean cancer?
Certain cancers, particularly lymphomas and leukaemias, can cause drenching sweats, fever and unexplained weight loss. These symptoms are non-specific and may also occur with infection, inflammatory disease and endocrine disorders.
Features that require assessment
- persistent enlarged lymph nodes;
- unexplained enlargement of the spleen;
- unintentional weight loss;
- persistent fever;
- unusual bruising or bleeding;
- marked fatigue or pallor;
- recurrent infections;
- ongoing unexplained symptoms.
Investigation may involve
- physical examination;
- full blood count and blood film;
- inflammatory markers;
- liver and kidney testing;
- chest imaging where indicated;
- ultrasound or CT in selected cases;
- specialist referral or tissue sampling.
Avoid interpreting one symptom in isolation
The probability of a serious cause depends on age, duration, examination findings, weight change, fever, lymph nodes, blood results and associated symptoms.
How a clinician assesses persistent night sweats
Clarifying the sweating pattern
The clinician will ask how often episodes occur, whether clothing or bedding becomes soaked, whether the room is cool and how long the problem has been present.
Reviewing associated symptoms
Fever, cough, weight loss, diarrhoea, pain, swollen glands, palpitations, snoring, breathing pauses and daytime sleepiness help guide investigation.
Checking medicines and risk factors
The assessment may cover menopause, diabetes, alcohol, medication changes, immune suppression, travel, tuberculosis exposure and recent infections.
Examination and targeted testing
Physical examination and investigations are selected according to the likely causes and warning features rather than using the same test panel for every patient.
Information that can help
Symptom severity
Mild dampness differs from sweating that requires changing clothes or bedding.
Documented temperature
Recording temperature during an episode may help distinguish a hot flush from febrile illness.
Objective weight change
Recorded weight measurements are more useful than a general impression of weight loss.
Respiratory symptoms
Cough, sputum, haemoptysis, chest pain and breathlessness may indicate a pulmonary cause.
Medication changes
New prescriptions, dose increases, supplements and non-prescription substances should be mentioned.
Sleep symptoms
Snoring, witnessed apnoeas, choking, insomnia and daytime sleepiness may suggest sleep-disordered breathing.
What tests may be used to investigate night sweats?
| Investigation | What it may assess | When it may be considered |
|---|---|---|
| Full blood count | Anaemia, infection, platelet abnormalities or blood-cell disorders | Persistent symptoms, fatigue, pallor, bruising or recurrent infection |
| CRP or ESR | Evidence of inflammation or infection | Fever, pain, weight loss or suspected inflammatory disease |
| Liver and kidney tests | Organ function and systemic illness | General investigation or before selected treatments |
| Thyroid function | Hyperthyroidism or other thyroid dysfunction | Heat intolerance, tremor, palpitations or weight change |
| Glucose or HbA1c | Diabetes or possible hypoglycaemia risk | Diabetes treatment, nocturnal symptoms or metabolic risk |
| HIV testing | HIV infection and associated risks | According to symptoms, exposure and clinical assessment |
| TB testing | Latent infection or active tuberculosis | Persistent cough, fever, weight loss, exposure or travel risk |
| Chest X-ray | Pneumonia, TB, a mass or another chest abnormality | Persistent cough, breathlessness, chest pain, haemoptysis or systemic symptoms |
| CT imaging | More detailed assessment of the chest, abdomen or another body region | Abnormal initial tests, persistent symptoms or specialist concern |
| Microbiology | Bacterial, mycobacterial, fungal or viral infection | Sputum production, fever, travel or suspected infection |
| Sleep study | Obstructive sleep apnoea and overnight breathing disturbance | Loud snoring, witnessed apnoeas, gasping, choking, unrefreshing sleep or daytime sleepiness |
Imaging is not automatically required
Many patients can initially be assessed through history, examination and targeted blood tests. Chest X-ray or CT is used when symptoms, risk factors or initial findings justify imaging.
How are night sweats managed?
Management depends on the underlying cause. Environmental measures may improve comfort but do not replace investigation when episodes are persistent or associated with warning symptoms.
Keep the bedroom cool
Improve ventilation, use a fan where appropriate and select lighter bedding.
Choose breathable fabrics
Cotton or moisture-wicking sleepwear and layered bedding may be easier to change during an episode.
Reduce personal triggers
Alcohol, caffeine, spicy foods and strenuous exercise close to bedtime can worsen sweating in some people.
Review medicines
A clinician may adjust the dose, timing or type of medicine when treatment is the likely cause.
Treat hormonal symptoms
Menopausal symptoms may respond to hormonal or non-hormonal treatment after individual assessment.
Prevent low glucose
Diabetes treatment may need adjustment when nocturnal hypoglycaemia is confirmed.
Treat infection
Treatment depends on the organism and may involve antibiotics, antivirals, antifungals or specialist therapy.
Treat obstructive sleep apnoea
Appropriate OSA treatment may improve sleep quality and associated nocturnal sweating in affected patients.
Manage anxiety
Psychological therapy, stress management and appropriate medical treatment may reduce autonomic arousal.
General sleep habits may improve comfort and recovery. Read the London Chest Specialist guide to sleep hygiene and improving sleep quality .
Treat the cause rather than the sweating alone
Cooling measures can make sleep more comfortable, but persistent unexplained night sweats should be managed according to the diagnosis rather than repeatedly suppressed without assessment.
When might respiratory assessment be helpful?
Respiratory review may be appropriate when:
- a cough persists for more than three weeks;
- breathlessness is unexplained or worsening;
- there is recurrent or persistent fever;
- you have blood-stained sputum;
- chest infections keep returning;
- chest imaging is abnormal;
- TB or fungal infection is being considered;
- standard treatment has not resolved symptoms.
Sleep assessment may be appropriate when:
- snoring is loud and habitual;
- breathing pauses are witnessed;
- you wake choking or gasping;
- sleep remains unrefreshing;
- you experience morning headaches;
- concentration or memory is affected;
- you feel excessively sleepy during the day;
- sleepiness affects driving safety.
A persistent cough can have infectious and non-infectious causes. Learn more about chronic cough diagnosis and specialist assessment .
Frequently asked questions
What counts as a true night sweat?
True night sweats generally soak clothing or bedding despite a cool sleeping environment. Mild perspiration beneath heavy bedding is not necessarily abnormal.
Are night sweats always a sign of serious illness?
No. Menopause, medicines, anxiety, alcohol, low glucose and environmental heat are common causes. Persistent episodes or warning symptoms still require assessment.
Can menopause cause drenching night sweats?
Yes. Menopausal hot flushes can be severe enough to soak sleepwear or bedding and significantly disrupt sleep.
Can antidepressants cause night sweats?
Yes. Several antidepressant classes can increase sweating. Speak to the prescriber rather than stopping treatment abruptly.
Can low blood sugar cause sweating during sleep?
Yes. Nocturnal hypoglycaemia may cause sweating, shaking, disturbed dreams or morning headache, particularly in people using insulin or certain diabetes medicines.
Can obstructive sleep apnoea cause night sweats?
OSA can be associated with frequent nocturnal sweating. Suspicion is greater when sweating occurs with loud snoring, breathing pauses, gasping, unrefreshing sleep or daytime sleepiness. A sleep study is needed for diagnosis.
Do night sweats mean I have tuberculosis?
Not by themselves. TB is more concerning when night sweats accompany persistent cough, fever, weight loss, reduced appetite, haemoptysis or relevant exposure.
What blood tests may be performed?
Testing is individualised but may include a full blood count, inflammatory markers, liver and kidney tests, thyroid function, glucose and targeted infection tests.
Will I need a chest X-ray or CT scan?
Not automatically. Imaging is more likely when respiratory symptoms, fever, weight loss, examination findings or initial test results suggest a chest condition.
When should I seek urgent help?
Seek urgent help for coughing up blood, severe breathlessness, chest pain, fainting, confusion or rapidly worsening illness. Call 999 for severe or life-threatening symptoms.
Conclusion
Night sweats are common and have many possible causes. Menopause, medicines, anxiety, environmental overheating, alcohol and low blood glucose are among the most frequent explanations.
Obstructive sleep apnoea is another possible cause, particularly when sweating occurs with loud snoring, witnessed breathing pauses, gasping, unrefreshing sleep or daytime sleepiness.
Persistent or drenching episodes should be interpreted alongside the wider clinical picture. Fever, unexplained weight loss, persistent cough, haemoptysis, diarrhoea, swollen glands or marked fatigue can indicate the need for further investigation.
Assessment starts with a careful history, examination and medicine review. Blood tests, infection testing, chest imaging or a sleep study may then be selected according to the likely cause.
Management focuses on the underlying diagnosis. Cooling the bedroom, choosing breathable bedding and avoiding personal triggers can improve comfort but should not delay assessment when symptoms are persistent or concerning.
References and further information
- NHS. Night sweats. Read NHS guidance
- National Institute for Health and Care Excellence. Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s. View NICE guideline NG202
- Arnardottir ES, Janson C, Bjornsdottir E, et al. Nocturnal sweating—a common symptom of obstructive sleep apnoea: the Icelandic Sleep Apnoea Cohort. View the BMJ Open study
- NHS. Symptoms of menopause and perimenopause. Read about menopausal symptoms
- NHS. Tuberculosis. Read NHS tuberculosis guidance
- National Institute for Health and Care Excellence. Suspected cancer: recognition and referral. View NICE guideline NG12
- London Chest Specialist. Obstructive sleep apnoea and snoring. Read the sleep apnoea guide
- London Chest Specialist. Chest infection diagnosis and treatment. Explore the chest infection service
- London Chest Specialist. Chronic cough assessment. Read about chronic cough
- London Chest Specialist. Sleep hygiene and insomnia. Read the sleep-hygiene guide
Night Sweats With Cough, Snoring or Breathing Symptoms?
A respiratory consultation can review your symptom pattern, medicines, infection risks, travel history, sleep symptoms and whether chest imaging, a sleep study or targeted investigations are appropriate.
