Author: Kirsty Brownlie, general practitioner, Bristol. Reviewed and updated by the OnMedica editorial team.

This quick guide* covers the key points for GPs on the assessment of night sweats, and answers the following questions:

1. What are the potential underlying causes?
2. What red-flag features do clinicians need to be aware of?
3. What assessments and investigations should be carried out?
4. How to investigate a patient with no clear cause for night sweating?

NB The guide focuses on night sweats (nocturnal hyperhidrosis) and does not cover primary hyperhidrosis.

*This quick guide is deliberately concise and readers are strongly recommended to refer to the references listed at the end of the quick guide.

Night sweats: introduction

• Night sweating is a common presenting complaint in primary care, with a reported prevalence of between 10% and 41% in the primary care setting¹ – It is a symptom commonly linked to menopause, malignancies, autoimmune diseases, gastro-oesophageal reflux disease and infections, but is also often reported by individuals who do not have these conditions^1,2
• The diverse range of possible underlying causes (from idiopathic to malignant) can make tackling this symptom daunting for clinicians, and worrying for patients – see Box 1 for the wide variety of potential causes
• There may be a clear cause for night sweating indicated from early assessment and this will prompt appropriate treatment
• In many cases there will be no obvious cause for symptoms, and there is currently no formal guidance from NICE or SIGN available regarding the investigation and management of patients with night sweats
• This guide suggests an approach to further assessing these patients, based on the limited evidence that is currently available

1. What are the potential underlying causes of night sweats?

Night sweats have been associated with an extensive list of conditions, see Box 1. Taking a careful history can allow subsequent examination and investigations to be tailored to the potential underlying cause.

When assessing a patient with night sweats, it is helpful to have an understanding of common differential diagnoses and the features associated with these, for example:

• Patients may present with symptoms suggestive of a viral (e.g. influenza or COVID-19) or bacterial infection, which can then be managed appropriately
• Other common causes include obesity; malignancy (there may be other red-flag features such as weight loss, malaise and localising symptoms); autoimmune and connective tissue disorders (possible indicators include skin, joint and nail symptoms and systemic features); menopause (suggested by menstrual irregularities and vasomotor symptoms in women); certain medications (see Box 2); and more complex infections such as HIV or tuberculosis (travel, social and sexual history may raise suspicion about these)
• Alternatively, the history may point to a psychological cause, e.g. anxiety, post-traumatic stress disorder or even night terrors. Obviously, if an environmental cause is suspected, then advice should be tailored as appropriate.

^{*More common possible underlying causes of night sweats
GORD=gastro-oesophageal reflux disease; HIV=human immunodeficiency virus; PTSD=post-traumatic stress disorder}

^{GnRH=gonadotropin-releasing hormone; NSAIDs=non-steroidal anti-inflammatory drugs; PDE5=phosphodiesterase type 5; SSRIs=selective serotonin reuptake inhibitors}

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2. What red-flag features do clinicians need to be aware of?¹

Red-flag features that clinicians should consider when assessing a patient who presents with a history of night sweats include:

• Reduced appetite or weight loss
• Chest pain/palpitations
• Haemoptysis/Persistent cough
• Fatigue/malaise
• Foreign travel
• GI symptoms
• High-risk sexual behaviour
• History of alcohol excess or recreational drug use
• Pruritus
• Skin rashes/joint symptoms  
• Swellings, deformities or lumps (particularly lymphadenopathy)
• Symptoms suggestive of COVID-19
• Symptoms warranting a 2-week-wait referral

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3. What assessments and investigations should be carried out?

Take a full history

A clinician needs to rule out any serious underlying disease in a patient with night sweats, so the initial consultation should be focused on this aim.

• Identify any red-flag features (see above) for prompt investigation or urgent referral to an appropriate speciality
• Rule out external overheating at the outset – ask whether:
  • other household members have experienced night sweats
  • the affected person has tried to adjust their sleep attire or bedding to alleviate symptoms (if yes then this should be taken seriously)
• Evaluate the severity of symptoms:
  • How many times do the symptoms wake the person from sleep?
  • Does the bed linen need to be changed?
• Depending on the age of a female patient, assess:
  • menopausal features such as vasomotor symptoms, vaginal dryness, urogenital symptoms or mood changes
  • relationship of symptoms to menstrual cycle (night sweats are common around the time of menstruation)
  • whether the patient is postpartum or breastfeeding
• Exclude febrile illness as many common self-limiting conditions may result in sweating which is particularly noticeable at night
  • Ask the patient to take their temperature and record details in a symptom diary, which may be useful during follow up
• Night sweats are a classical feature of tuberculosis and lymphoma – ask specifically about symptoms suggestive of these conditions
• Ask about symptoms of obstructive sleep apnoea and gastro-oesophageal reflux disease
• Ask about any urinary symptoms (especially for older male patients which may suggest a prostate disorder)
• Examine the patient’s medical history to highlight potential causes, for example does the patient have:
  • diabetes – is this nocturnal hypoglycaemia?
  • a history of malignancy – could this be recurrent disease?
• Take a thorough drug history, including OTC and internet-purchased medicines – see Box 2 for commonly used drugs that may induce night sweats
• Ask patients about their mental health including any depressive or anxiety symptoms
• Investigate family history:
  • Are there any rare conditions that have a strong genetic link which the patient may be unaware of?
• Ask about their social history, including:
  • recent travel, sexual contacts, alcohol/smoking and recreational drug use, pets, occupation, and any unwell contacts

Examine the patient

• Make a general assessment of whether the patient appears well or unwell and whether there is any cachexia or pallor
• Examine according to any localising symptoms or features elicited from the history
• Carry out a thorough physical assessment including:
  • cardio-respiratory and abdominal examinations (check for masses or organomegaly)
  • inspection of the skin and joints
  • palpation for lymphadenopathy (examine neck, axilla and inguinal region)
  • examination of the ears, nose, mouth and throat
• Consider breast examination for females and prostate for male patients.

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4. How to investigate a patient with no clear cause of night sweating?

In many cases there may be no symptoms or signs to direct additional investigations and no clear cause for night sweating. A clinician must decide how comprehensively and urgently to look for occult pathology, based on their own clinical acumen and the patient’s degree of anxiety.

See Box 3 for a suggested approach on how to investigate patients with no clear cause for their symptoms, and with no positive findings to suggest underlying pathology at each stage in the process. NB this is a guide only, and clinicians should use their own discretion regarding how far to probe for disease.

^{BG=blood glucose; BMI=body mass index; CRP=C-reactive protein; CT=computed tomography; FBC=full blood count; FIT=faecal immunochemical test; FSH/LH=follicle-stimulating hormone/luteinising hormone; GAD-7=Generalised Anxiety Disorder scale 7-item; HbA1c=glycated haemoglobin; HIV=human immunodeficiency virus; LFTs= liver function tests; MSU=midstream specimen of urine; PCR=polymerase chain reaction; TFTs=thyroid function tests; U&Es=urea and electrolytes}  

If the results of initial investigations are inconclusive, further investigation will depend on the clinician’s suspicion of serious underlying disease. Table 1 summarises the signs and symptoms of some illnesses that may present with night sweats.

Table 1. Signs and symptoms of illnesses that may present with night sweats^1,3

^{GORD=gastro-oesophageal reflux disease; HIV=human immunodeficiency virus; TB=tuberculosis}

Additional practical advice

• Management is very much dictated by the underlying cause, if this is revealed on assessment
• Adopt a watchful waiting approach in patients with no associated symptoms, no red flags and no positive findings on history, examinations and investigations – provide clear advice that the patient should seek medical attention if there are any new symptoms, or if their night sweats become worse
• It can be useful to ask patients to keep a diary of symptoms covering a period of time
• Provide advice regarding keeping cool at night as this may help symptoms
• If appropriate, arrange a follow up appointment to check the patient’s progress at a later date either to review a symptom diary or to discuss investigations

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References

1. Bryce C. Persistent Night Sweats: Diagnostic Evaluation. Am Fam Physician. 2020 Oct 1;102(7):427-433.
2. Mold J, et al. Night sweats: a systematic review of the literature. J Am Board Fam Med. Nov–Dec 2012;25(6):878–93.
3. Night sweats – causes. Mayo Clinic Symptom Guide, March 2022.
4. British National Formulary. Accessed 06 May 2022.
5. Ting S. Drug-induced hyperhidrosis. DermNet NZ, 2020.

Patient information

• Night sweats. Patient.info, 2018
• Night sweats. NHS website, 2022

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