Night sweats are a common complaint, affecting an estimated 10-40% of adults at some point. While sometimes the cause is as simple as a too-warm bedroom or too many blankets, persistent or severe night sweats warrant investigation. They can be an early warning sign of hormonal changes, thyroid dysfunction, infections, blood disorders, and other conditions that benefit from early detection and treatment.

The body maintains core temperature within a narrow range through a sophisticated thermoregulation system. Sweating is the primary cooling mechanism — when body temperature rises, sweat glands are activated to release fluid that evaporates and carries heat away from the skin. When this system is triggered inappropriately or excessively during sleep, night sweats result.

This article explores why night sweats occur, what underlying conditions might be responsible, and what blood tests can help identify the cause.

Understanding Night Sweats

It’s important to distinguish true night sweats from simply feeling warm at night. This distinction matters because true night sweats often signal an underlying medical condition worth investigating, while simply being warm at night is usually environmental.

True night sweats are severe — they drench sleepwear and bedding, not just cause mild dampness. People with true night sweats often wake up needing to change their pajamas and sometimes their sheets. The sweating occurs regardless of room temperature and isn’t explained by too many blankets, synthetic bedding that doesn’t breathe, or an overheated bedroom. True night sweats represent a physiological response — the body’s temperature regulation system activating inappropriately or excessively during sleep.

Feeling warm at night, in contrast, is often environmental — the room is too warm, there are too many covers, or the bedding material doesn’t allow adequate heat dissipation. This causes discomfort but not the drenching sweats of true night sweats. Simply adjusting the environment typically resolves the problem.

Of course, there’s a spectrum between these extremes, and even moderate night sweating that disrupts sleep is worth addressing.

How the body regulates temperature:

Your body’s thermoregulation system is controlled by the hypothalamus, a small but crucial region of the brain that acts as the body’s thermostat. The hypothalamus receives temperature information from sensors throughout the body — in the skin, internal organs, and the blood flowing through the brain itself. When it senses that body temperature is rising above the set point (normally around 98.6°F/37°C), it orchestrates cooling responses.

The primary cooling mechanism is sweating. Sweat glands in the skin release fluid that evaporates from the skin surface, carrying heat away with it. Each gram of sweat that evaporates removes about 580 calories of heat. Additionally, blood vessels in the skin dilate to bring more warm blood to the surface where heat can radiate away.

This system is remarkably precise under normal circumstances, maintaining core temperature within a narrow range despite varying ambient temperatures and activity levels. But when something disrupts this system, inappropriate sweating can result.

What causes the thermostat to malfunction:

Night sweats can occur through several mechanisms:

• The hypothalamic set point is altered: Various conditions can change the temperature threshold at which sweating is triggered. Hormonal changes (particularly declining estrogen in menopause) make the hypothalamus more sensitive to small temperature fluctuations, causing it to trigger cooling responses at temperatures that would normally be perceived as normal. Infections and inflammatory conditions can raise the set point (fever), after which sweating occurs when the fever “breaks.” Certain medications affect neurotransmitters that modulate the hypothalamic thermostat.
• Body temperature actually rises: Infections and inflammatory conditions cause true elevation of body temperature (fever) as part of the immune response. When the fever breaks — often at night when immune activity cycles — sweating occurs as the body works to bring temperature back down to normal. This is appropriate sweating in response to actual temperature elevation.
• Metabolic rate increases: Conditions that increase the body’s metabolic rate — most notably hyperthyroidism — cause excess heat production. The body generates more heat than it can easily dissipate, triggering compensatory sweating. This tends to cause both daytime and nighttime sweating.
• Autonomic nervous system dysfunction: The autonomic nervous system controls sweating (along with heart rate, blood pressure, digestion, and other involuntary functions). Dysfunction of this system — from diabetes, neurological conditions, or other causes — can result in inappropriate sweating that doesn’t correlate with temperature.
• Stress hormone release: Conditions that trigger stress hormone release (adrenaline, cortisol) can cause sweating. Hypoglycemia (low blood sugar) is a prime example — the body perceives low blood sugar as a threat and mounts a stress response that includes sweating. Nightmares, anxiety, and sleep apnea episodes can also trigger stress responses with sweating.
• Medications affecting neurotransmitters: Many medications — particularly antidepressants — affect the neurotransmitter systems (serotonin, norepinephrine) that help regulate body temperature and sweating. This can result in excessive sweating as a side effect.

Characteristics to note:

When evaluating night sweats, documenting certain details helps identify the cause and guide appropriate testing:

Severity — how bad are the sweats?

• Mild — feeling warm, slight dampness, maybe throwing off covers
• Moderate — sweating through sleepwear, needing to change clothes
• Severe — drenching sweats, sheets soaked, need to change both clothes and bedding

Severe, drenching night sweats are more likely to have a significant underlying cause than mild dampness.

Frequency — how often do they occur?

• Occasional — once a week or less
• Frequent — several times per week
• Nightly — every night or nearly every night

Frequent or nightly sweats warrant more thorough evaluation than occasional episodes.

Duration — how long has this been happening?

• Recent onset — started in the past few weeks
• Months — going on for several months
• Years — long-standing problem

Also note if they’re getting better, worse, or staying the same. New-onset or worsening night sweats deserve more urgent attention.

Associated symptoms — what else is going on?

• Fever or chills — suggests infection or inflammatory process
• Unintentional weight loss — concerning for serious underlying disease
• Fatigue — common with many causes but particularly concerning if severe
• Daytime sweating as well — suggests systemic cause rather than just nighttime phenomenon
• Flushing or hot flashes — typical of hormonal causes
• Rapid heartbeat or palpitations — may suggest thyroid or cardiac cause
• Anxiety or tremor — consider thyroid dysfunction or anxiety disorders
• Swollen lymph nodes — concerning for infection or lymphoma
• Cough or respiratory symptoms — consider TB or other infections

Timing and triggers — is there a pattern?

• Time of night — early night vs. early morning sweats may have different causes. Early morning sweats might suggest hypoglycemia (blood sugar drops overnight).
• Relationship to menstrual cycle — women may notice sweats at certain points in the cycle
• Relationship to meals — reactive hypoglycemia typically causes symptoms 2-4 hours after eating; a heavy dinner could trigger early morning hypoglycemia
• New medications — consider medication side effects
• Alcohol consumption — alcohol can trigger sweats and also causes hypoglycemia
• Stress or anxiety — may trigger autonomic sweating

When to be concerned:

Night sweats warrant medical evaluation when they are:

• Severe — drenching sweats, not just mild dampness
• Persistent — lasting more than a few weeks without obvious explanation
• Accompanied by unexplained weight loss — this combination is a red flag for serious disease
• Accompanied by fever — suggests infection or inflammatory process
• Accompanied by enlarged lymph nodes — concerning for lymphoma or infection
• Occurring with fatigue that doesn’t improve with rest — may indicate underlying disease
• Representing a significant change from your normal — new symptoms deserve attention
• Significantly impacting sleep quality and daily functioning — quality of life matters
• Accompanied by other unexplained symptoms — clusters of symptoms warrant evaluation

Red flags requiring prompt evaluation:

The combination of night sweats with certain other symptoms is concerning and warrants prompt medical attention:

• Unexplained weight loss (especially more than 10% of body weight): Along with night sweats and fever, this “B symptom” triad is classic for lymphoma and other serious conditions
• Persistent fever: Fever lasting more than a few days without clear cause needs evaluation
• Swollen lymph nodes that persist or grow: Particularly if painless — concerning for lymphoma
• Severe, progressive fatigue: Not just tiredness but debilitating fatigue
• Bone pain: May indicate bone marrow involvement or metastatic disease
• Cough lasting more than 3 weeks, especially with blood: Concerning for TB or lung cancer
• Recent travel to areas with endemic infections: TB, malaria, and other infections may present with night sweats
• Easy bruising or unusual bleeding: May suggest blood disorder

Hormonal Causes: The Most Common Explanation

Hormonal changes are the most frequent cause of night sweats, particularly in women during perimenopause and menopause. However, hormonal factors can affect anyone at various life stages, and understanding the hormonal basis of night sweats helps guide appropriate testing and treatment.

Menopause and perimenopause:

The menopausal transition is the most common cause of night sweats in women over 40, affecting up to 75-85% of women to some degree. As ovarian function gradually declines in the years leading up to menopause (perimenopause) and after the final menstrual period (menopause), estrogen levels fluctuate erratically and eventually decrease, profoundly affecting the hypothalamus and its temperature regulation function.

How estrogen affects thermoregulation:

Estrogen helps regulate the hypothalamic thermostat — the thermoneutral zone, which is the range of body temperatures the hypothalamus considers “normal” and doesn’t trigger heating or cooling responses. With adequate estrogen, this zone is relatively wide. When estrogen levels fluctuate or decline, the thermoneutral zone narrows dramatically. Small changes in core body temperature that previously would have been ignored now trigger vigorous cooling responses — blood vessel dilation (causing the flushing and warmth of a hot flash) and sweating.

This explains why women often experience sudden, intense hot flashes and sweating with only minor temperature triggers. The hypothalamus is essentially overreacting to normal temperature variations because its regulatory settings have been disrupted by changing estrogen levels.

Characteristics of menopausal night sweats:

• Often accompanied by hot flashes during the day: Night sweats are essentially hot flashes occurring during sleep. Most women who have night sweats also have daytime hot flashes, though some notice sweats primarily at night.
• Begin in perimenopause: Night sweats typically start in perimenopause — the 2-10 years before the final menstrual period — when hormone fluctuations are most dramatic. Periods may still be occurring (though often irregular) when symptoms begin.
• May continue for years: The average duration of hot flashes and night sweats is about 7 years, but they can persist much longer — even 10+ years for some women. Some women have symptoms well into their 60s or 70s.
• Intensity varies: Some women have mild, occasional symptoms that are merely annoying. Others have severe, frequent episodes that significantly disrupt sleep, impair quality of life, and affect work performance and relationships. About 25% of women have symptoms severe enough to seek treatment.
• Associated with other menopausal symptoms: Night sweats often occur alongside other symptoms of the menopausal transition — mood changes, irritability, difficulty concentrating, sleep disturbance (beyond what the sweats cause), vaginal dryness, and changes in libido.
• Pattern may change over time: Night sweats may be most intense early in the menopausal transition and gradually diminish, though this varies considerably.

The timing and severity vary greatly between women, and we don’t fully understand why some women have severe symptoms while others sail through menopause with minimal discomfort. Factors that may influence severity include genetics, smoking (smokers have worse symptoms), higher body mass index (though the relationship is complex), ethnicity, stress, and overall health.

Other hormonal causes:

Premature ovarian insufficiency (POI): When normal ovarian function is lost before age 40 (affecting about 1% of women), it causes menopausal symptoms — including night sweats and hot flashes — at an earlier age than expected. POI may occur spontaneously (idiopathic), after cancer treatment (chemotherapy, radiation), due to autoimmune conditions, or from genetic factors. Women with POI experience the same hormonal disruption as natural menopause, just earlier.

Surgical menopause: Removal of both ovaries (bilateral oophorectomy), often performed along with hysterectomy, causes abrupt, complete estrogen loss. Unlike natural menopause where hormone levels decline gradually, surgical menopause creates sudden hormone withdrawal, often triggering more severe hot flashes and night sweats than natural menopause. Younger women undergoing surgical menopause are particularly affected.

Androgen deficiency in men: While less dramatic and well-known than menopause, declining testosterone levels can cause hot flashes and night sweats in some men. This may occur naturally with aging (sometimes called “andropause” or late-onset hypogonadism) or as a result of medical treatments. Androgen deprivation therapy (ADT) for prostate cancer — which reduces testosterone to castrate levels — commonly causes hot flashes and sweating, affecting up to 80% of men on this treatment. Surgical castration (orchiectomy) has similar effects.

Pregnancy and postpartum: The dramatic hormonal shifts of pregnancy and the postpartum period can cause night sweats. During pregnancy, increased blood volume and metabolic rate can cause sweating. Postpartum night sweats are very common in the first few weeks after delivery — they’re sometimes called “postpartum sweats” — as hormone levels plummet from their pregnancy highs and the body also eliminates excess fluid accumulated during pregnancy. These typically resolve within a few weeks but can be quite dramatic.

Menstrual cycle fluctuations: Some women experience night sweats at specific points in their menstrual cycle, typically around ovulation (when estrogen drops temporarily) or in the late luteal phase just before menstruation (when both estrogen and progesterone decline). This is more common in women with premenstrual syndrome (PMS) or premenstrual dysphoric disorder (PMDD).

Hormone-producing tumors: Rare tumors that produce hormones can cause flushing and sweating. Carcinoid tumors may cause carcinoid syndrome with flushing, diarrhea, and wheezing. Pheochromocytoma (adrenal tumor producing adrenaline) causes episodic sweating, rapid heartbeat, and elevated blood pressure.

What to test:

FSH (Follicle-Stimulating Hormone): FSH rises as ovarian function declines. In menopause, FSH is typically elevated because the pituitary is working hard to stimulate ovaries that are no longer responding adequately. However, in perimenopause, FSH fluctuates widely and a single measurement may not be definitive.

Estradiol: The primary estrogen. Low estradiol confirms reduced estrogen production. However, levels fluctuate significantly in perimenopause — a woman might have low estradiol one week and higher levels the next.

Testosterone: In men with suspected androgen deficiency, low testosterone (particularly with elevated FSH and LH) confirms hypogonadism. Morning testosterone levels are most accurate as levels naturally fluctuate through the day.

Note on hormone testing: For the classic menopausal woman in her late 40s or 50s with typical symptoms, hormone testing isn’t always necessary — the clinical picture may be sufficient for diagnosis. However, testing may be helpful in younger women where premature ovarian insufficiency is possible, when the diagnosis is uncertain, or when specific hormone levels would influence treatment decisions.

Thyroid Dysfunction

Thyroid disorders, particularly hyperthyroidism, are important causes of night sweats that are readily identified through blood testing. The thyroid gland controls metabolic rate throughout the body, and disorders of thyroid function directly affect heat production and temperature regulation.

Hyperthyroidism:

Hyperthyroidism (overactive thyroid) occurs when the thyroid gland produces too much thyroid hormone, increasing metabolic rate throughout the body. This revs up cellular processes in every tissue, generating excess heat as a byproduct and triggering sweating both day and night.

How hyperthyroidism causes night sweats:

• Increased basal metabolic rate: Excess thyroid hormone accelerates metabolism in every cell, generating more heat. The body is essentially running “hot” all the time.
• Enhanced catecholamine sensitivity: Thyroid hormone increases the body’s sensitivity to adrenaline and similar hormones, amplifying stress responses including sweating.
• Altered thermoregulation: The hypothalamic set point may be affected, triggering cooling responses at lower thresholds.
• Increased cardiac output: The heart beats faster and harder, generating more heat.

Characteristics of hyperthyroid night sweats:

• Heat intolerance during the day as well: Unlike menopausal hot flashes which are episodic, hyperthyroid heat intolerance and sweating tend to be more constant. People feel warm most of the time, not just in discrete episodes.
• Skin often feels warm and moist: On examination, the skin is typically warm and there may be visible moisture.
• Associated with characteristic hyperthyroid symptoms: Weight loss despite good or increased appetite (the hypermetabolic state burns calories), rapid heartbeat or palpitations, tremor (fine trembling of the outstretched hands), anxiety, irritability, nervousness, difficulty sleeping (even without sweats), increased bowel movements or diarrhea, menstrual irregularities in women, muscle weakness.
• May have visible signs: Thyroid enlargement (goiter) may be visible or felt in the neck. In Graves’ disease (the most common cause of hyperthyroidism), characteristic eye changes may occur — bulging eyes (exophthalmos), staring appearance, lid retraction.

Hyperthyroidism has several causes, with Graves’ disease (an autoimmune condition where antibodies stimulate the thyroid) being the most common. Other causes include toxic nodular goiter, thyroiditis (inflammation of the thyroid), and excessive thyroid hormone intake.

Hashimoto’s thyroiditis fluctuations:

Hashimoto’s thyroiditis, the most common cause of hypothyroidism, is an autoimmune condition that gradually destroys the thyroid gland. However, the course isn’t always straightforward. During active inflammation, stored thyroid hormone may be released from damaged cells, causing transient hyperthyroid phases — sometimes called “hashitoxicosis.” During these phases, people may experience sweating, palpitations, anxiety, and other hyperthyroid symptoms, even though the overall trajectory is toward hypothyroidism.

This can create a confusing clinical picture where symptoms fluctuate. Eventually, Hashimoto’s typically leads to permanent hypothyroidism requiring thyroid hormone replacement.

What to test:

TSH (Thyroid-Stimulating Hormone): The primary screening test for thyroid dysfunction. In hyperthyroidism, TSH is suppressed (low) because excess thyroid hormone signals the pituitary to stop stimulating the thyroid. A suppressed TSH is the first clue to hyperthyroidism.

Free T4 and Free T3: Measure the actual circulating thyroid hormones. In hyperthyroidism, one or both are elevated. Some patients have “T3 toxicosis” where T3 is elevated but T4 is normal.

TPO antibodies: Present in both Hashimoto’s and often in Graves’ disease. Help identify autoimmune thyroid disease.

TSI (Thyroid-Stimulating Immunoglobulin): Specifically indicates Graves’ disease — these antibodies mimic TSH and stimulate the thyroid.

Blood Sugar Problems

Hypoglycemia (low blood sugar) triggers a powerful stress response that includes sweating. For people with diabetes on insulin or certain oral medications, nocturnal hypoglycemia is an important and often overlooked cause of night sweats.

How hypoglycemia causes sweating:

The brain depends almost entirely on glucose for fuel. When blood sugar drops too low, the brain perceives this as a serious threat — and it is. The body responds by releasing counter-regulatory hormones, particularly adrenaline (epinephrine) and cortisol, which work to raise blood sugar but also cause a constellation of warning symptoms.

Adrenaline triggers the classic hypoglycemic symptoms:

• Sweating — often profuse
• Trembling or shakiness
• Rapid heartbeat (tachycardia)
• Anxiety or feeling of doom
• Hunger
• Pallor

These symptoms are the body’s warning system, urging you to eat something and raise your blood sugar. They’re protective — recognizing and responding to these symptoms prevents blood sugar from dropping to dangerous levels.

Nocturnal hypoglycemia:

Hypoglycemia occurring during sleep is particularly problematic because the warning symptoms may not fully wake the person. Night sweats may be the most obvious sign that hypoglycemia has occurred.

Signs of nocturnal hypoglycemia:

• Drenching night sweats: Waking in sweat-soaked clothing or bedding
• Restless sleep: Tossing, turning, sleep talking, or unusual movements during sleep
• Nightmares: Vivid, often frightening dreams
• Waking with rapid heartbeat or anxiety: The adrenaline response may wake you
• Morning headache: Common after overnight hypoglycemia
• Waking feeling unrested, confused, or “hungover”: Neuroglycopenic symptoms from the brain having been deprived of adequate glucose
• High fasting blood sugar (paradoxically): The counter-regulatory hormones can cause rebound hyperglycemia — known as the Somogyi effect — so morning blood sugar may actually be high despite overnight lows

People may not wake during hypoglycemic episodes, especially if they have impaired hypoglycemia awareness (common in long-standing diabetes, where the warning symptoms become blunted), are taking beta-blockers (which block some of the adrenaline-mediated symptoms), or have consumed alcohol (which impairs both hypoglycemia awareness and glucose production).

Who’s at risk for nocturnal hypoglycemia:

• People with diabetes taking insulin: Particularly intermediate or long-acting insulin given in the evening, or if dinner or evening snack is inadequate
• People taking sulfonylurea medications: Glipizide, glyburide (glyburide is particularly problematic), glimepiride — these stimulate insulin release and can cause hypoglycemia especially if meals are skipped
• People who skip meals or eat irregularly: Insufficient evening food with active diabetes medication overnight
• People who exercise vigorously: Exercise increases insulin sensitivity and glucose use; if insulin doses aren’t adjusted, overnight lows can occur
• People who drink alcohol: Alcohol inhibits glucose production by the liver and impairs awareness of hypoglycemia. Evening alcohol consumption is a common cause of nocturnal hypoglycemia.
• People with variable schedules: Irregular meal timing and insulin dosing increases hypoglycemia risk

Reactive hypoglycemia:

Some people without diabetes experience hypoglycemia 2-4 hours after eating, particularly after high-carbohydrate meals. This is called reactive (or postprandial) hypoglycemia. The mechanism involves an exaggerated insulin response to carbohydrate intake — the pancreas releases more insulin than needed, overshooting and driving blood sugar too low.

If a high-carbohydrate dinner triggers reactive hypoglycemia in the early morning hours, it could cause night sweats. Symptoms include sweating, shakiness, anxiety, and hunger, and are relieved by eating.

What to test:

Fasting glucose: Screens for diabetes and can detect fasting hypoglycemia (though nocturnal lows may not be reflected in morning fasting glucose, especially if rebound hyperglycemia occurs).

HbA1c: Reflects average blood sugar over 2-3 months. Helps assess overall diabetes control. Paradoxically, a very low HbA1c in someone on insulin may suggest frequent hypoglycemia.

Fasting insulin: May help evaluate reactive hypoglycemia or, in rare cases, identify insulin-producing tumors (insulinoma).

Continuous glucose monitoring (CGM): For suspected nocturnal hypoglycemia in diabetes, CGM is invaluable — it captures glucose levels throughout the night and can show exactly when lows occur.

Infections

Infections, both acute and chronic, are important causes of night sweats. The classic triad of night sweats, fever, and unintentional weight loss is concerning for chronic infection or malignancy.

How infections cause night sweats:

When the immune system fights infection, it releases cytokines — signaling molecules that help coordinate the immune response. Some cytokines (particularly interleukin-1, interleukin-6, and tumor necrosis factor) act on the hypothalamus to raise the body’s temperature set point, causing fever. As the fever breaks — often at night when the immune response cycles — sweating occurs to bring temperature back down.

Tuberculosis:

Night sweats are a classic symptom of tuberculosis (TB), particularly pulmonary TB. The combination of night sweats, weight loss, persistent cough, and sometimes bloody sputum is concerning for TB. TB should be considered especially in people with:

• Travel to or residence in high-prevalence areas
• Exposure to someone with TB
• HIV infection or other immunocompromised states
• Homelessness or incarceration history

HIV infection:

Night sweats can occur with acute HIV infection (seroconversion illness) or with advanced HIV disease. Testing should be considered in anyone with unexplained night sweats, particularly with other risk factors.

Endocarditis:

Infection of the heart valves (endocarditis) can cause night sweats along with fever, fatigue, and weight loss. Risk factors include abnormal heart valves, IV drug use, and recent dental procedures.

Osteomyelitis and abscesses:

Deep-seated infections (bone infections, internal abscesses) may present with night sweats and fever, sometimes without obvious localizing symptoms.

Other infections:

Various other infections can cause night sweats, including:

• Fungal infections (histoplasmosis, coccidioidomycosis)
• Malaria (cyclical fevers and sweats)
• Brucellosis
• Mononucleosis

What to test:

Complete blood count: May show elevated white blood cells (infection) or abnormalities suggesting other conditions.

ESR and CRP: Inflammatory markers that are elevated with infection and inflammation.

HIV testing: Should be considered in unexplained night sweats.

Blood cultures: If bacterial infection (like endocarditis) is suspected.

TB testing: Tuberculin skin test or interferon-gamma release assay (IGRA) if TB is suspected.

Malignancy

Night sweats can be an early symptom of certain cancers, particularly lymphomas. While cancer is not the most common cause of night sweats, it’s an important one to consider, especially when sweats are severe, persistent, and accompanied by other concerning symptoms.

Lymphoma:

Night sweats are one of the “B symptoms” of lymphoma (along with fever and unexplained weight loss). Both Hodgkin lymphoma and non-Hodgkin lymphoma can present this way. The sweats are typically severe — drenching — and occur regularly.

Leukemia:

Some leukemias, particularly chronic leukemias, can cause night sweats along with fatigue, easy bruising, and recurrent infections.

Other cancers:

Various other malignancies can cause night sweats through:

• Tumor-produced cytokines affecting the hypothalamus
• Hormone-producing tumors (pheochromocytoma, carcinoid)
• Metabolic effects of advanced cancer

Warning signs:

Night sweats are more concerning for malignancy when accompanied by:

• Unintentional weight loss (especially >10% of body weight)
• Persistent unexplained fever
• Enlarged lymph nodes (especially painless)
• Easy bruising or bleeding
• Persistent fatigue
• Bone pain

What to test:

Complete blood count with differential: Can show abnormalities suggesting leukemia or lymphoma (abnormal white cell counts, anemia, low platelets).

LDH (Lactate Dehydrogenase): Often elevated in lymphoma and other cancers.

ESR and CRP: May be elevated with malignancy.

If blood tests suggest a hematologic malignancy or if clinical suspicion is high, imaging (CT scans) and possibly lymph node biopsy may be recommended.

Medications

Many medications can cause night sweats as a side effect. If night sweats began after starting a new medication, the medication should be considered a potential cause.

Common culprits:

Antidepressants: Among the most common medication causes of night sweats. SSRIs (sertraline, fluoxetine, paroxetine), SNRIs (venlafaxine, duloxetine), and tricyclic antidepressants can all cause sweating, sometimes severely.

Hormone therapies:

• Tamoxifen and aromatase inhibitors (breast cancer treatment)
• GnRH agonists (prostate cancer treatment, endometriosis treatment)
• Hormone replacement therapy (paradoxically, during dose adjustments)

Diabetes medications: Insulin and sulfonylureas can cause hypoglycemia and resultant sweating.

Antipyretics: Aspirin, acetaminophen, and NSAIDs can cause sweating as they reduce fever.

Other medications:

• Opioids
• Steroids
• Niacin
• Nitrates
• Sildenafil and similar medications

Medication withdrawal:

Withdrawal from alcohol, opioids, or benzodiazepines can cause severe sweating, often worse at night.

Other Causes of Night Sweats

Obstructive sleep apnea:

Sleep apnea — repeated breathing interruptions during sleep — is associated with night sweats. The mechanism may involve the stress response to airway obstruction and hypoxia (low oxygen). Treating sleep apnea often improves night sweats.

Consider sleep apnea if night sweats occur with:

• Snoring
• Witnessed breathing pauses during sleep
• Waking gasping or choking
• Excessive daytime sleepiness despite adequate sleep time
• Morning headaches

Anxiety disorders:

Anxiety and panic disorder can cause sweating, including at night. Nocturnal panic attacks may cause sudden awakening with intense fear, rapid heartbeat, and drenching sweats.

Gastroesophageal reflux disease (GERD):

Severe reflux at night can cause sweating along with heartburn and disrupted sleep.

Autonomic dysfunction:

Conditions affecting the autonomic nervous system (which controls sweating) can cause inappropriate sweating. This includes diabetic autonomic neuropathy and other conditions.

Idiopathic hyperhidrosis:

Some people have excessive sweating without identifiable cause. While this more commonly affects daytime sweating (particularly palms, soles, and underarms), it can include night sweats.

The Testing Strategy for Night Sweats

Blood tests can identify many underlying causes of night sweats. The appropriate tests depend on the clinical picture and associated symptoms.

Core tests for evaluating persistent night sweats:

Complete blood count (CBC): Screens for infection, anemia, and blood cell abnormalities that might suggest leukemia or lymphoma.

Thyroid function (TSH): Screens for hyperthyroidism, a common treatable cause.

Blood glucose (fasting glucose, HbA1c): Identifies diabetes (associated with hypoglycemia) or blood sugar abnormalities.

Inflammatory markers (ESR, CRP): Elevated with infection, inflammation, and some malignancies.

Additional tests based on clinical suspicion:

• Hormone levels (FSH, estradiol, testosterone): If menopausal or hormonal cause suspected
• HIV testing: Should be considered, especially with risk factors or other unexplained symptoms
• TB testing: If tuberculosis risk factors present
• LDH: If lymphoma or other malignancy suspected
• Free T4 and T3: If TSH abnormal
• Blood cultures: If bacterial infection (endocarditis) suspected

What to Do With the Results

If thyroid dysfunction is found:

Hyperthyroidism is treated with medications (methimazole, propylthiouracil), radioactive iodine, or surgery. Night sweats typically resolve as thyroid levels normalize.

If hormonal changes are confirmed:

Options for menopausal night sweats include hormone replacement therapy (most effective), non-hormonal medications (SSRIs, gabapentin, clonidine), and lifestyle modifications. Treatment depends on symptom severity and individual risk factors.

If blood sugar abnormalities are found:

Diabetes management may need adjustment to prevent nocturnal hypoglycemia. This might involve changing medication timing, adjusting doses, or modifying evening eating patterns.

If inflammatory markers are elevated:

Further investigation is needed to identify the cause — infection workup, imaging, or specialist referral depending on the clinical picture.

If blood count abnormalities are found:

Abnormalities suggesting leukemia or lymphoma require hematology referral for further evaluation and possible bone marrow biopsy.

When Tests Are Normal

Normal blood tests are reassuring and rule out many serious causes, but don’t explain all night sweats:

• Environmental factors: Room too warm, too many blankets, synthetic bedding that doesn’t breathe
• Medications: Review all medications for sweating as a side effect
• Sleep apnea: Requires sleep study for diagnosis, not blood tests
• Anxiety: May not show on standard blood work
• Perimenopausal changes: Hormone levels fluctuate and may be normal when tested
• Idiopathic: Sometimes no cause is found despite thorough evaluation

Lifestyle Approaches for Managing Night Sweats

While identifying and treating the underlying cause is most important for lasting relief, these practical strategies can help reduce night sweats and minimize their impact on sleep quality:

• Optimize your sleep environment: Keep your bedroom cool — most sleep experts recommend 65-68°F (18-20°C) for optimal sleep. Use air conditioning or a fan. Consider a ceiling fan that provides continuous air circulation. Use breathable bedding materials — cotton, linen, bamboo, or specifically designed moisture-wicking fabrics work better than synthetic materials that trap heat. Choose lightweight blankets or use layers that can easily be removed. Consider cooling pillows or mattress toppers designed to dissipate heat.
• Wear appropriate sleepwear: Choose light, loose-fitting sleepwear made from breathable, moisture-wicking fabrics. Cotton is a classic choice; modern moisture-wicking athletic materials work well too. Some people find sleeping nude more comfortable if privacy allows. Keep a change of clothes nearby for convenience if you do wake up drenched.
• Avoid known triggers before bed: Alcohol, while it may help you fall asleep initially, disrupts sleep architecture and can trigger night sweats — it’s also a common hypoglycemia trigger. Spicy foods can increase body temperature and trigger sweating. Caffeine can affect sleep and may contribute to sweating. Heavy, large meals before bed increase metabolic heat production. Hot beverages or hot baths immediately before bed can raise body temperature.
• Maintain a healthy weight: Excess weight is associated with increased sweating (more insulation trapping body heat) and also with sleep apnea, which can cause night sweats. Weight loss may reduce night sweats from multiple causes.
• Exercise regularly: Regular physical activity helps regulate body temperature and improves sleep quality. However, avoid vigorous exercise close to bedtime, as the temporary increase in body temperature and metabolism can disrupt sleep and potentially trigger sweating.
• Practice stress management: Stress and anxiety can contribute to night sweats through autonomic nervous system activation. Relaxation techniques — meditation, deep breathing, progressive muscle relaxation, yoga — may help, especially if anxiety is a contributing factor. A consistent, calming bedtime routine can help reduce stress-related sleep disruption.
• Keep water by the bed: Sweating causes fluid loss. Having water readily available helps you rehydrate without fully waking or getting out of bed. Consider keeping a small towel nearby as well.
• Use layered bedding: Rather than one heavy comforter, use multiple layers that can easily be adjusted throughout the night. This allows you to fine-tune your temperature without fully waking.
• Consider bedroom humidity: Very dry air can sometimes exacerbate sweating as the body tries to regulate temperature. A humidifier might help in very dry environments, though this is very individual.
• Track patterns: Keep a simple log of when night sweats occur, their severity, what you ate and drank, exercise, stress levels, and for women, menstrual cycle timing. Patterns may emerge that help identify triggers or provide useful information for your healthcare provider.

These measures can provide meaningful relief for many people with night sweats, though they’re most effective as part of a comprehensive approach that includes identifying and treating underlying causes when present.

The Bottom Line

Night sweats that are severe, persistent, or accompanied by other symptoms often have identifiable underlying causes that blood testing can help reveal. While waking up warm or slightly damp is common and usually benign, true drenching night sweats — soaking through sleepwear and bedding — warrant medical attention, particularly when they occur regularly or are accompanied by weight loss, fever, or other concerning symptoms.

Hormonal changes, particularly menopause, are the most common cause of night sweats in women over 40. The fluctuating and declining estrogen levels of the menopausal transition affect the hypothalamic thermostat, triggering sweating at normal body temperatures. While this is a natural process, effective treatments are available for those with severe symptoms.

Thyroid dysfunction — especially hyperthyroidism — is another important treatable cause. The excess thyroid hormone increases metabolic rate and heat production, causing sweating both day and night. A simple TSH test can screen for this condition.

Blood sugar problems, particularly nocturnal hypoglycemia in people with diabetes, trigger stress hormone release and sweating. This is important to recognize because it indicates a need to adjust diabetes management.

More serious causes, including infections (TB, HIV) and malignancies (lymphoma), are less common but important to consider, especially when night sweats occur with weight loss, fever, or enlarged lymph nodes. Blood testing can screen for many of these conditions.

Don’t forget medications — many common medications, especially antidepressants, can cause night sweats as a side effect. If night sweats started after beginning a new medication, discuss this possibility with your healthcare provider.

A basic blood workup including complete blood count, thyroid function (TSH), blood sugar markers (fasting glucose, HbA1c), and inflammatory markers (ESR, CRP) can screen for most medically significant causes of night sweats. Additional testing for hormones, infections, or other conditions may be warranted based on the clinical picture.

Don’t ignore severe or persistent night sweats. Early identification of the underlying cause allows for appropriate treatment and, in most cases, meaningful improvement in symptoms and sleep quality.

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Key Takeaways

• True night sweats are drenching — soaking sleepwear and bedding, not just feeling warm
• Menopause is the most common cause in women over 40 — related to estrogen fluctuation affecting the hypothalamic thermostat
• Hyperthyroidism is an important treatable cause — increases metabolism and heat production; screened with TSH
• Nocturnal hypoglycemia causes sweating — particularly in people with diabetes on insulin or sulfonylureas
• Infections can cause night sweats — TB, HIV, and other infections should be considered
• The triad of night sweats, weight loss, and fever is concerning — warrants thorough evaluation for infection or malignancy
• Many medications cause night sweats — particularly antidepressants and hormone therapies
• Sleep apnea is associated with night sweats — consider if snoring or daytime sleepiness present
• Blood testing can identify most serious causes — CBC, TSH, glucose, and inflammatory markers are key
• Lifestyle modifications help — cool room, breathable bedding, avoiding triggers