A fever is a temporary rise in body temperature, usually caused by the immune system responding to an infection. A temperature of 38°C or above is commonly considered a fever, although the person’s age, symptoms and overall condition are more important than the number alone.
Common causes
Viral infections are common causes of fever. Bacterial infections, inflammatory conditions, heat-related illness, some medicines and vaccinations can also raise temperature. Fever itself is a symptom rather than a diagnosis, and antibiotics do not help viral infections.
Care at home
- Rest and drink regularly to reduce the risk of dehydration.
- Wear comfortable, light clothing and keep the room at a normal temperature.
- Acetaminophen or ibuprofen may be used for discomfort when suitable, following the label or professional advice.
- Do not use cold baths or excessive cooling that causes shivering.
- Stay away from others when an infectious illness is likely.
Do not give aspirin to anyone under 16. Ibuprofen is not suitable for everyone, including some people with kidney, stomach or bleeding problems. Children should be given age-appropriate products and doses.
Fever in babies and children
Seek urgent medical advice for a temperature of 38°C or above in a baby under three months, or 39°C or above in a baby aged three to six months. A child also needs assessment if fever lasts five days, they are drinking or urinating much less, or their behavior or breathing is concerning.
When adults should seek medical advice
Seek advice when fever is worsening, not improving with home care, repeatedly returns, or occurs in pregnancy, after recent surgery or international travel, or in someone with a weakened immune system or serious long-term condition. Persistent fever with severe localised pain, a new rash or dehydration also needs assessment.
Emergency warning signs
Get immediate help for difficulty breathing, confusion, extreme drowsiness, a seizure, a stiff neck, severe headache, blue or grey skin, a rash that does not fade under pressure, collapse or inability to drink. Emergency assessment is also needed when very high temperature follows heat exposure and the person is confused or has hot skin, as this may be heatstroke.
Sources
Reviewed: 28 August 2026