Lymphoma (particularly Hodgkin's lymphoma) classically presents with night sweats, fever, and weight loss (B-symptoms) — the majority of patients are aged 15–35 or >65. The 5-year survival for Hodgkin's lymphoma caught early is >90%, dropping significantly with delayed diagnosis. TB remains a common cause of night sweats in the UK, particularly in urban areas and immigrant populations — the UK has one of the highest TB rates in Western Europe. HIV can cause night sweats at any stage — always offer testing. Infective endocarditis is the must-not-miss cardiac cause.

The definition of "true night sweats" is critical — studies show many patients presenting with "night sweats" are experiencing normal thermoregulation in a warm bedroom, not pathological sweating. The qualifier "soaking through clothes requiring a change" has a much higher positive predictive value for organic pathology. SSRIs and SNRIs are the most common drug cause of night sweats in UK primary care — a medication review before investigation can avoid unnecessary testing. The menopausal history is the highest-yield question in women aged 45–55.

Menopause and drug side effects account for the majority of night sweats in primary care — the key diagnostic task is efficiently excluding the dangerous minority (lymphoma, TB, HIV). Obstructive sleep apnoea causes night sweats through arousal-induced sympathetic activation and is frequently overlooked — relevant questions include snoring, witnessed apnoeas, daytime sleepiness, and obesity. Nocturnal hypoglycaemia in diabetics on sulphonylureas or insulin is a serious and completely reversible cause that requires medication review. Phaeochromocytoma is rare (1 in 100,000) but is a must-not-miss cause of episodic sweating with headache and hypertension.

Lymph node examination is the highest-yield component of the physical examination for night sweats — rubbery, non-tender, matted nodes in a young person with weight loss and night sweats is Hodgkin's lymphoma until proven otherwise. Hepatosplenomegaly is a key examination finding that markedly increases the probability of haematological malignancy or systemic infection. Documenting and comparing serial weights is more sensitive than asking patients "have you lost weight?" — patients often underestimate significant weight loss.

LDH (lactate dehydrogenase) is an inexpensive and underutilised investigation — an elevated LDH in the context of night sweats, weight loss, and lymphadenopathy is a haematological emergency until lymphoma is excluded. HIV testing should be offered to all patients presenting with unexplained night sweats (NICE HIV testing guidelines 2016) — UK guidance recommends routine HIV testing in all general practices in areas of high prevalence. CXR is the single most cost-effective screening investigation for both TB and lymphoma. Phaeochromocytoma is best screened with plasma free metanephrines (sensitivity >97%) — urine catecholamines have lower sensitivity.

The 2WW haematology pathway is specifically designed for lymphoma — do not wait for specialist availability if B-symptoms are present. CT scanning and bone marrow biopsy for staging are time-critical. TB in primary care requires mandatory notifiable disease reporting (Public Health England/UKHSA) and contact tracing — do not delay referral. Identifying OSA as a cause of night sweats is highly impactful — CPAP treatment eliminates both sweating and the significant cardiovascular and mortality risk of untreated OSA.

HRT is the most effective treatment for menopausal night sweats with an NNT of approximately 3. The safety concerns around HRT have been significantly revised following re-analysis of the WHI study — for most women under 60 or within 10 years of menopause, HRT benefits outweigh risks. Transdermal oestrogen does not increase VTE risk and is preferred over oral oestrogen. Venlafaxine and gabapentin are evidence-based alternatives for women where HRT is contraindicated (breast cancer, personal preference) — NICE menopause guideline NG23 (2023 update) explicitly recommends these. SSRIs are paradoxically both a cause and treatment of menopausal sweats — SNRIs (venlafaxine) have stronger evidence.

CBT for menopausal hot flushes (the MENOS trials) has demonstrated significant reduction in hot flush frequency and bother scores — comparable to pharmacological alternatives for women who cannot or choose not to use HRT. It should be offered alongside, not instead of, HRT discussion. Alcohol consistently emerges as a modifiable risk factor in population studies — this is an underemphasised lifestyle intervention. Environmental cooling is inexpensive, safe, and immediately effective for any cause of night sweats while investigations are awaited.

Night sweats with a negative initial workup require a structured safety-net — lymphoma can present insidiously with a normal initial blood panel. A persistent unexplained night sweat at 3 months should prompt repeat investigations and CT consideration, even without new symptoms. HIV test results require active follow-up — some patients do not return for results. The annual HRT review is mandated by NICE NG23 (2023) — cardiovascular risk assessment, breast awareness, and reassessment of ongoing need are all components.