True night sweats are not the same as feeling warm under the duvet.
Doctors reserve the term for episodes heavy enough to soak sleepwear or bedding, and the Cleveland Clinic describes them as much more intense than ordinary sweating.
The American Academy of Family Physicians defines them as drenching sweats that force a change of bedclothes and recommends a workup when the pattern persists.
The list of possible causes is longer than most people realize.
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Hormonal shifts
Perimenopause and menopause are the most common driver in women during midlife.
Hot flashes often continue through the night and are one of the recognized hormonal causes of nighttime sweating.
Sleep-disrupting episodes warrant a conversation with a doctor, especially when they last for years or become severe.
Low testosterone
Men experience their own version of vasomotor flushing.
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Cleveland Clinic lists hot flashes among the symptoms of low testosterone, defining low levels as below 300 nanograms per deciliter, with male hypogonadism diagnosed when those low levels appear alongside matching symptoms.
It is a commonly overlooked cause of nighttime sweating in older men, and a blood test can confirm it.
Nighttime low blood sugar
Nocturnal hypoglycemia is a well-known trigger.
The National Institute of Diabetes and Digestive and Kidney Diseases warns that people with diabetes treated with insulin or sulfonylureas can lose the usual warning signs of low blood sugar.
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Sweating through the sheets may be the first clue.
Vivid dreams, morning headaches and restless sleep often accompany it.
Lymphoma and other blood cancers
Cancer clinicians group unexplained weight loss, fever and drenching night sweats together as "B symptoms," and Cleveland Clinic hematologists rely on them when diagnosing and staging lymphoma.
The pattern applies to Hodgkin and non-Hodgkin lymphoma and to some leukemias.
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Any one of the three in isolation is rarely cancer, but the combination is a reason to see a doctor promptly.
Tuberculosis and serious infections
The CDC lists persistent cough with blood or sputum, fever, loss of appetite, weight loss and sweating at night as the most common features of active TB.
Bacterial infections such as endocarditis, an inflammation of the heart lining, produce the same picture.
Flu, COVID-19 and other viral infections can also trigger night sweats while the body fights the illness.
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Obstructive sleep apnea
Repeated pauses in breathing during sleep set off surges in the sympathetic nervous system, the branch that also controls the sweat glands.
Cleveland Clinic notes that sleep apnea and other nervous-system problems can lead to night sweats.
Loud snoring, morning headaches and daytime fatigue are often the other clues.
Anxiety, panic and PTSD
Chronic stress and anxiety disorders can trigger sweating during sleep, according to Cleveland Clinic, and panic attacks that occur overnight can leave someone drenched on waking.
Post-traumatic stress disorder, with its recurrent nightmares, can produce the same picture.
Medication side effects
A number of everyday drugs can be the culprit.
Antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), are among the most common.
Cleveland Clinic also flags blood pressure medications, some migraine drugs, narcotic pain medication, ibuprofen, steroids and breast cancer treatments.
Fever reducers taken at bedtime can produce the same effect.
When to see a doctor
Cleveland Clinic advises anyone whose night sweats disrupt sleep to schedule a visit.
The combination that most concerns physicians is night sweats together with unexplained weight loss, swollen lymph nodes or persistent fever.
When those appear together, a same-week appointment with a primary care doctor is the right next step.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.