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The febrile patient
Fever is a clue, not a diagnosis. Decide quickly whether they are septic, then think about who the patient is — neutropenic, returning traveller, injecting drugs, immunosuppressed — because that changes what you look for and how fast you treat. Built for revision, not live patient decisions.
Settle them, and check the basics
is this sepsis?Red flags — what each should make you think
A normal temperature doesn't exclude serious infection — the elderly, the immunosuppressed and anyone on steroids or paracetamol may not mount a fever. Judge the patient by their NEWS2, their lactate and how they look, not by the thermometer.
If sepsis is suspected — act within the hour
- O₂Oxygen
- cxBlood cultures
- ℞IV antibiotics
- IVIV fluids
- lacLactate
- UOUrine output
Understand the patient & find the source
who are they? where is it?Who is the patient? It changes everything
- Neutropenic / on chemotherapy — treat on suspicion, antibiotics within 1 hour, before the count is back
- Returning traveller — malaria until proven otherwise; ask about dengue, typhoid, and viral haemorrhagic fever risk
- Injecting drug use — endocarditis, abscesses, septic arthritis, necrotising soft-tissue infection
- Splenectomy — overwhelming pneumococcal / meningococcal sepsis
- Transplant, biologics, steroids, HIV — atypical organisms, blunted signs
- Recent surgery or hospital stay — wound, line, collection, C. difficile, hospital-acquired pneumonia
Hunt the source
- Chest — cough, sputum, pleuritic pain, crackles
- Urine — dysuria, loin pain, catheter
- Abdomen — biliary, appendix, diverticular, collection
- Skin, soft tissue, lines, joints — cellulitis, wounds, cannula sites, hot joints
- CNS — headache, photophobia, confusion, rash
- Heart — new murmur, splinter haemorrhages, embolic phenomena
Not every fever is infection: PE, drugs (NMS, serotonin syndrome, drug fever), malignancy (lymphoma), vasculitis, thyroid storm, transfusion reactions, gout and pancreatitis can all cause fever.
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Fever (≥38°C) or any sign of sepsis within 6 weeks of chemotherapy (or other neutropenia). May look surprisingly well.
Neutrophils below 0.5 ×10⁹/L confirms — but don't wait for the count.
Empirical IV piperacillin–tazobactam (or local equivalent) within 1 hour of arrival, cultures, oncology/acute oncology team.
Fever after travel to an endemic area, usually within 3 months (up to a year). Headache, myalgia, D&V. Can deteriorate within hours.
Thick and thin films plus rapid antigen test; three negative sets over 48–72 h to exclude.
Severe (parasitaemia ≥2%, impaired consciousness, acidosis, AKI, ARDS, hypoglycaemia): IV artesunate and ITU. Discuss every case with infectious diseases.
Fever with a new murmur, prosthetic valve, IVDU, recent dental or invasive procedure; splinter haemorrhages, Janeway lesions, embolic stroke.
At least three sets of blood cultures from separate sites before antibiotics (if stable), echocardiogram. Modified Duke criteria.
Antibiotics per local/cardiology guidance; early cardiology and microbiology; surgery for heart failure, abscess or large vegetations.
Headache, neck stiffness, photophobia, confusion, seizures, focal signs, rash.
LP (unless contraindicated), blood cultures, meningococcal and HSV PCR.
Don't delay: IV ceftriaxone ± amoxicillin (over 60/immunocompromised for Listeria); IV aciclovir if encephalitis possible; dexamethasone per guidance.
Severe pain, rapid spread, systemic toxicity, crepitus, skin changes appearing late. IVDU, diabetes.
A surgical diagnosis — LRINEC can support but don't let imaging delay theatre.
Emergency surgical debridement, broad IV antibiotics including toxin cover (clindamycin), resuscitation.
Investigate — what to order, when, and what it tells you
test with a question in mindSepsis bloods
Find the source
Returning traveller
Always consider
How the plan comes together
disposition · handoverhome
Low NEWS2, clear minor source (e.g. simple UTI), eating and drinking, reliable follow-up.
Safety-net: worsening, confusion, rash, rigors, not passing urine → return.
admit / escalate
Possible sepsis, high-risk group, no source found, abnormal bloods, or traveller with a fever.
Hand over: source, timing of antibiotics, lactate trend, who the patient is.
Fever plus the right context is the diagnosis: chemotherapy means neutropenic sepsis, travel means malaria, and injecting drugs means endocarditis. Ask the context questions every time. Nicely done getting here.
Clerking template
copy or downloadThe febrile patient — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 12 knownFrequently asked questions
quick answersWhat are the red flags for the febrile adult?
- NEWS2 ≥5, or one parameter scoring 3 — think possible sepsis
- Chemotherapy in the last 6 weeks — think neutropenic sepsis — antibiotics within 1 h
- Travel to a malaria area in the last year — think falciparum malaria
- Injects drugs + new murmur — think infective endocarditis
- Headache, neck stiffness, confusion — think meningitis / encephalitis
- Pain out of proportion — think necrotising fasciitis
- Non-blanching rash — think meningococcal sepsis
- Antipsychotic or serotonergic drug + rigidity — think NMS / serotonin syndrome
What is the initial management of the febrile adult?
- Oxygen — target 94–98% (88–92% if at risk of hypercapnia)
- Blood cultures — before antibiotics, but never delay antibiotics for them
- IV antibiotics — per local policy, guided by the likely source
- IV fluids — balanced crystalloid bolus if hypotensive or lactate raised, then reassess
- Lactate — above 2 = concerning; above 4 = high risk
- Urine output — catheter if shocked; strict fluid balance
Always alongside senior support and your local guideline.
What diagnoses must you not miss in the febrile adult?
- Neutropenic sepsis — chemo · antibiotics within 1 h
- Falciparum malaria — traveller · may look well
- Infective endocarditis — murmur · emboli · IVDU
- Meningitis / encephalitis — headache · confusion · rash
- Necrotising fasciitis — pain out of proportion
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for the febrile adult?
- Sepsis bloods — At least two sets before antibiotics.
- Find the source — Dip and culture.
- Returning traveller — Films + rapid test; repeat x3.
- Always consider — In any unexplained fever or recurrent infection.
Admit or discharge: how is the plan decided for the febrile adult?
- Home — Low NEWS2, clear minor source (e.g. simple UTI), eating and drinking, reliable follow-up.
- Admit / escalate — Possible sepsis, high-risk group, no source found, abnormal bloods, or traveller with a fever.
Is there a clerking template for the febrile adult?
Yes — there is a clerking template for the febrile adult on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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