Overview
A fever means a raised body temperature, usually 38C or above. It is often a sign that the body is fighting an infection. The temperature matters, but other symptoms and how unwell someone looks are just as important.
How common is it?
Fever is one of the most common reasons people seek advice for themselves or their children.
Causes and risk factors
Fever is most often caused by infections such as colds, flu, tummy bugs, or throat infections. It can also happen after some vaccinations, with heat illness, or as a reaction to certain medicines.
Common risk factors
- Recent viral or bacterial infection
- Being a baby or young child
- A weakened immune system
- Long-term health problems that raise the risk from infection
- Recent vaccination
- Hot environments or heavy exertion
Symptoms
- A temperature of 38C or above
- Feeling hot, cold, or shivery
- Sweating
- Headache or muscle aches
- Tiredness or poor appetite
- In children, being less active or less interested in feeding
When to see a doctor
Urgent advice is needed for any baby under 3 months with a temperature of 38C or higher. Seek urgent help for a child aged 3 to 6 months with a temperature of 39C or higher, or for anyone with trouble breathing, confusion, a stiff neck, a non-fading rash, dehydration, chest pain, a seizure, or a fever that is getting worse instead of better.
Diagnosis
A thermometer can confirm a fever. Further tests depend on the likely cause and may include checking urine, swabs, blood tests, or scans if symptoms suggest a more serious illness.
Treatments
Fluids and rest
Drink enough fluids and rest. In children, regular small drinks are especially important to reduce the risk of dehydration.
Medicine for discomfort
Paracetamol or ibuprofen can help if the person feels uncomfortable, provided they are suitable for that age and situation. The aim is comfort, not forcing the temperature to normal.
Treating the cause when needed
Some causes need specific treatment, but antibiotics are only useful for selected bacterial infections and do not treat most fevers caused by viruses.
Self-care and lifestyle
- Rest and drink enough so urine stays pale
- Dress lightly and avoid overheating
- Check children regularly, including for signs of dehydration
- Do not give aspirin to children under 16
Prevention
Vaccinations, hand hygiene, and avoiding close contact with people who are unwell can reduce many common infections that cause fever.
Sources and review
Last reviewed: 20 July 2026 by Living Diabetes Editorial Team. This guide was checked against current patient and professional guidance. It is educational and does not replace care from your own healthcare team.