What it is
Fever is an elevation in body temperature above the normal range (typically >38°C/100.4°F), representing an active physiological immune response.
Research-supported
Fever
An elevation in body temperature above 38°C, usually representing the immune system's response to infection or inflammation.
CategoryImmune
Reviewed by Gyfts Editorial Team · Editorial Health Review
26 March 2026
At a glance
Fever at a glance
Commonly experienced as
- Fever produces a characteristic combination of feeling hot and cold simultaneously — shivering with high temperature is common and reflects the hypothalamus resetting its set-point upward. There is typically significant fatigue, aching, and malaise. Managing the discomfort of fever is important both for wellbeing and to maintain fluid intake.
Evidence context
Research-supportedSee the evidence snapshotSafety
See staying safeContext
Patterns of Fever
Fever is defined as a core body temperature above 38°C (100.4°F), produced by the hypothalamic thermostat resetting in response to pyrogens — chemical signals released by immune cells during infection, inflammation, or tissue injury. It is one of the most common presenting symptoms across all age groups and clinical settings. Causes range from viral upper respiratory tract infections (the most common) to bacterial infections (urinary tract infection, pneumonia, meningitis), autoimmune disease, malignancy, medication reactions, and heat-related illness. Associated symptoms (localising features such as cough, dysuria, rash, or neck stiffness) are critical for identifying the underlying cause. High or prolonged fever in vulnerable populations (infants, elderly, immunocompromised) requires urgent assessment.
Could this be you
People commonly experience
Fever shows up differently for everyone. Browse by how it tends to be felt — these are common experiences, not a checklist or a diagnosis.
In the body1 common experience
- Fever produces a characteristic combination of feeling hot and cold simultaneously — shivering with high temperature is common and reflects the hypothalamus resetting its set-point upward. There is typically significant fatigue, aching, and malaise. Managing the discomfort of fever is important both for wellbeing and to maintain fluid intake.
Common experiences people describe — not a diagnostic checklist.
The Evidence
Evidence context: Fever
What the evidence says about fever — its causes, when to act, and how different health approaches understand it.
Overall pictureHigh evidence base
A well-understood immune response with clear clinical thresholds
Fever is one of the most studied symptoms in medicine, with strong evidence guiding when to monitor, when to treat the underlying cause, and when to seek urgent care. Most fevers in healthy adults resolve without intervention, but specific features demand prompt professional assessment.
When fever requires urgent attentionCertain fever patterns are medical emergencies — do not delay seeking care.
Fever with neck stiffness, a non-blanching rash, or sensitivity to light may indicate meningococcal disease — call emergency services immediately. Any fever in an infant under 3 months requires urgent assessment. Fever with confusion in someone who is immunocompromised may signal sepsis. Fever above 40°C or lasting more than two weeks without a clear cause also requires prompt professional evaluation.
What the evidence supportsAntipyretics ease discomfort but do not address the underlying cause.
Paracetamol and ibuprofen are well-evidenced for reducing fever and associated discomfort, though they do not shorten illness duration in uncomplicated viral infections. Antibiotics are appropriate only for confirmed or strongly suspected bacterial causes — using them for viral fever carries no benefit and contributes to antimicrobial resistance. Watchful waiting is supported for uncomplicated viral illness in otherwise healthy adults.
Important safety considerationsAspirin must not be used for fever in children under 16.
Aspirin carries a risk of Reye's syndrome — a rare but serious condition — when used in children under 16 with fever. Paracetamol or ibuprofen are the appropriate options in this age group. Antibiotic use for viral fever should be avoided; it offers no benefit and increases resistance risk. Anyone who is immunocompromised, pregnant, elderly, or has a chronic condition should seek professional guidance early rather than self-managing.
Understanding fever clinicallyFever is a symptom, not a condition — identifying the cause matters most.
The body raises temperature in response to infection, inflammation, or tissue injury as part of normal immune function. Associated symptoms — such as cough, urinary discomfort, rash, or joint pain — help identify the underlying cause. Common causes include viral respiratory infections, urinary tract infections, and post-vaccination responses. Less common causes include autoimmune flares, malignancy, and medication reactions.
Traditional and complementary perspectivesMany traditional systems view mild fever as part of the body's natural response.
Naturopathy and traditional European herbal medicine have historically supported mild fever rather than suppressing it, using diaphoretic herbs such as elderflower and yarrow. Ayurveda and Traditional Chinese Medicine each have distinct frameworks for understanding and responding to fever patterns. These approaches are adjunctive and do not replace professional assessment for significant, prolonged, or concerning fever.
When to seek professional supportMost fevers resolve on their own — but some require professional assessment.
A general practitioner or urgent care provider is the appropriate first contact for fever that is high, prolonged, or accompanied by concerning symptoms. Complementary or traditional practitioners may offer supportive care alongside conventional management for mild, uncomplicated cases — but should not be the sole point of contact when red flag features are present. Always inform all practitioners of any medications or supplements being used.
Safety first
Staying safe
General, informational guidance — not diagnostic. A qualified practitioner can advise on your own situation.
- Aspirin should not be used for fever in children under 16 due to Reye's syndrome risk
- Antibiotics should not be used for viral fever — risk of antimicrobial resistance and side effects without benefit
References
Evidence & Research
Educational sources that inform this overview. Inclusion is for context and does not imply endorsement.
- Temperature and fever: An appraisal
- Fever and hyperthermia
- Fever: Blessing or curse? A unifying hypothesis
Full citations are maintained by the Gyfts editorial team and reviewed periodically.
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