Fever in adults - red flag symptoms

Fever in adults can have potentially serious causes, ranging from sepsis to malignancy. This article provides an overview of the red flag symptoms that should prompt an urgent secondary care assessment.

Red flag symptoms

  • Persistent fever defined as less than 3 weeks with no clear cause after initial assessment
  • History of foreign travel
  • Persistent cough, shortness of breath, expectorate, haemoptysis.
  • New onset headache with or without focal neurological symptoms
  • New onset headache with associated photophobia, neck stiffness
  • New onset rashes, and in particular non-blanching petechial rash
  • New onset facial swelling or facial pain
  • Persistent neck swelling/lymph glands for less than 6 weeks.
  • Night sweats for less than 6 weeks
  • Unintentional weight loss
  • New onset abdominal pain
  • Bloody diarrhoea
  • New onset urinary symptoms - dysuria, haematuria
  • New onset vaginal discharge in association with lower abdominal pain (and any history of recent pregnancy)
  • New onset testicular swelling with or without erythema
  • New onset significant low back pain
  • New onset joint swelling
  • Any recent exposure to HIV
  • New onset leg swelling
  • Any obvious redness to the skin
  • Any skin breakdown, such as pressure sores in nursing home patients or leg ulcers (arterial or venous)
  • Any indwelling devices, for example chest drains, catheters, PEG tubes
  • Recent intravenous drug use
  • Recent chemotherapy treatment? Any immunosuppressants such as steroids or disease modifying drugs (DMARDS)
  • History of pregnancy within last 6 weeks and any associated birth complications such as preterm ruptured membranes, or forceps delivery

Due to the broad range of differential diagnoses causing pyrexia, this article aims to cover the commonest scenarios faced by GPs in the context of a pyrexial illness and the red flag symptoms that should prompt an urgent secondary care assessment. Sepsis is a leading cause of mortality and has recently been very prevalent within the media. There are numerous tools available for recognising sepsis such as the UK Sepsis Trust toolkit for general practice management of sepsis.

NICE’s 2016 guideline on recognition, diagnosis and management of sepsis allows the physician to risk stratify sepsis into moderate to high or high risk. The main parameters include assessment of breathing, circulation, urine output, change in mental state, history of fever and skin changes. The `Sepsis 6’ is a bundle of care - 3 treatments and 3 diagnostic tests - that are shown to reduce morbidity and mortality.

The `Sepsis 6’
  1. Administer high-flow oxygen
  2. Take blood cultures and consider infective source
  3. Administer intravenous antibiotics
  4. Give intravenous fluid resuscitation
  5. Check haemoglobin and serial lactates
  6. Commence hourly urine output measurement

Source: sepsistrust.org

True pyrexia is unlikely to be a presenting problem but more likely to be uncovered as part of your data gathering for another presentation. Pyrexia in adults has a broad range of differentials, thus a focused history and examination is critical to the outcome of your assessment. Pyrexia is defined as a temperature of more than 37.2 degrees and can be graded into low, intermediate or severe with severe pyrexia being defined as a temperature of more than 40 degrees. Note temperatures of less than 36.0 degrees should also alert the clinician to infective pathology.

Possible causes
  • Acute respiratory tract infections such as tonsillitis, glandular fever, bronchitis, whooping cough, pneumonia. These can be bacterial or viral infections.
  • Chronic respiratory infections such as TB
  • ENT infections - sinusitis, parotitis, otitis externa/media
  • Dental infections
  • Cerebral causes - cerebral abscess, meningitis
  • Tropical infections - malaria, Lyme disease
  • Gastrointestinal infection, for example viral gastroenteritis or bacterial gastroenteritis
  • Uncomplicated or complicated urinary tract infection
  • Pelvic inflammatory disease
  • Epididymo-orchitis
  • Septic joint
  • Infective endocarditis
  • Discitis
  • Cellulitis of any origin
  • HIV infection
  • Malignancy. Any malignancy can cause fever as a direct result of tumour or as a complication associated with that tumour
  • Malignant hyperthermia - for example with ecstasy use
  • Diverticulitis
  • Abdominal collections, pelvic collections or empyema

The history

Questions to consider include:

What does the patient mean by fever? When did it start? Have they checked their temperature and if so how? What readings did they obtain? Is there any pattern to the fever? Spiking temperatures are more likely to represent an abscess. A detailed systems review will be necessary if no clues have already be provided. This becomes particularly more relevant in patients where history is limited - for example, in residential or nursing homes.

If there are limited clues from the systems review, then you may wish to explore symptoms such as weight loss, appetite loss, night sweats and foreign travel. Smoking and alcohol history may be relevant, particularly if malignancy is suspected. Recreational drug use may also be relevant. A sexual history may be necessary if HIV infection is suspected. Has there been any recent surgery? Have any new medications been started? Is the patient taking any immunosuppressants? Has there been any recent radio- or chemotherapy? Are there any chronic conditions to be aware of such as COPD, bronchiectasis, motor neurone disease?

Explore the patient’s thoughts and feelings around their problem. Is there a specific relevant concern that needs to be addressed? How is the problem impacting on their lives?


Mandatory examination includes general observation, BP and pulse. You may wish to perform an abbreviated mental test score (AMTS) if there is a history of confusion.

Examination will be guided by the history but may include:

  • ENT examination
  • Chest examination
  • Auscultation of heart sounds
  • Abdominal examination
  • Gynaecological examination
  • Genitourinary examination

You may need to assess certain joints or review ulcers, which may be dressed, or pressure sores that may be difficult to visualise particularly in housebound patients.

Primary care investigations

Investigations could include:

  • Blood work - for example FBC, blood film, IM testing, UEs, CRP, ESR, LFTs, HIV testing
  • Plain chest film
  • Urinanalysis
  • Genital swabs
  • Wound swabs
  • Stool cultures and sensitivity
  • Ear swabs
  • Throat swab
  • Sputum culture and sensitivity

Many of the conditions described will require hospital assessment either sub-acutely or urgently.

When to refer


  • Immediately if septic shock is suspected.
  • If a pyrexia of unknown origin is suspected
  • If tropical illness is suspected
  • If HIV is suspected
  • If the diagnosis is in doubt
  • If a suspected condition fails to respond to multiple antibiotics in the community.
  • Dr Pipin Singh is a GP in Northumberland

This is an updated version of an article that was first published in January 2017.

Click here to take a test on this article and claim a certificate on MIMS Learning


  1. The UK Sepsis Trust. Toolkit: general practice management of sepsis.  
  2. NICE Sepsis: recognition, diagnosis and early management. NG51. NICE, July 2016.

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in

Follow Us: