As temperatures soar during the recent heatwave, experts have urged people not to overlook persistent, heavy night sweats as merely a consequence of warm weather. While it is common to sweat when a bedroom is hot or bedding is too thick, consistently waking with soaked nightclothes and sheets-even in a cool room-may suggest an underlying health issue.
Dr Jiri Kubes, radiation oncologist and medical director of the Proton Therapy Center, emphasised that the pattern and duration of sweating, rather than sweating alone, should alert individuals. He explained, “Almost everyone experiences warmer, more uncomfortable nights during a heatwave, which can easily mask symptoms that might otherwise cause concern. The key question is whether there is a clear reason for the sweating. If the room temperature is cool, yet you consistently wake with pyjamas and bedding drenched, this differs from feeling mildly clammy on a hot night.”
Medically significant night sweats are typically severe enough to disrupt sleep or require a change of clothes or bedding. Dr Kubes cautioned that one or two sweaty nights during a heatwave rarely indicate a serious problem. However, if unexplained night sweats persist for more than two or three weeks, it is advisable to see a GP.
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He added, “Seek medical advice sooner if the sweating is severe or comes with other worrying symptoms. There is no need to wait several weeks if you feel significantly unwell.”
Drenching night sweats can be linked to certain blood cancers, particularly lymphoma, where they are part of the so-called “B symptoms,” which also include unexplained fever and significant unintended weight loss. Dr Kubes stressed the importance of considering additional symptoms: “Night sweats accompanied by unexplained weight loss, persistent fatigue, recurring fevers, or painless swelling in the neck, armpit, or groin should prompt a discussion with a doctor.”
Nevertheless, cancer is far from the most common cause. Night sweats have a variety of potential triggers, such as menopause, anxiety, an overactive thyroid, alcohol consumption, and certain medications including antidepressants, steroids, and some painkillers.
Infections may also be responsible, though less commonly in the UK; for example, tuberculosis can cause night sweats. Additionally, low blood sugar might induce sweating in those taking insulin or certain diabetes medications.
People should remain vigilant for painless lumps or swellings that do not resolve, unexplained itching, breathlessness, persistent cough, unusual bruising, or recurring infections. According to Dr Kubes, “Enlarged lymph nodes often occur as the body fights infection and usually return to normal. However, a painless swelling that persists or grows warrants medical evaluation. Similarly, while tiredness is common during a heatwave, it becomes concerning if it is severe, lasts a long time, and is accompanied by symptoms like drenching sweats, fever, or weight loss.”
Anyone who regularly wakes with soaked nightclothes or bedding should consult their GP, particularly if these symptoms are distressing or associated with other unexplained changes. Dr Kubes reassured, “Most people experiencing night sweats will not have cancer, and these symptoms alone do not provide a diagnosis. Conditions like an overactive thyroid are relatively common and treatable and can be identified through appropriate testing.”
His overall message is clear: people should not panic after a few hot nights but should recognise persistent and unexplained changes, especially when other warning signs are present. “Do not simply wait for the weather to cool if sweating is severe, recurring, or linked with other symptoms. Discussing the issue with your GP can help determine if further investigation is necessary,” he concluded.