High Fever

Overview

A fever is a temporary rise in body temperature, most often as part of the body's response to infection. Normal body temperature is around 37 degrees Celsius (98.6 degrees Fahrenheit), with some natural variation. A high fever generally means a temperature around 39 to 40 degrees Celsius (102 to 104 degrees Fahrenheit) or above.

Fever itself is usually a sign that the immune system is working, not a disease on its own. The height of a fever does not always match how serious the illness is. What matters most is how the person looks and behaves, any accompanying symptoms, and their age. A high fever in a young infant, or one with warning signs, needs prompt attention even when the cause seems minor. A fever may also be measured under the arm, in the ear, or on the forehead, and readings can vary slightly between methods, so it is the overall picture that counts most.

Common Causes

High fevers most often come from infections, but other causes exist:

• Viral infections: Influenza, COVID-19, and many childhood viruses commonly cause high temperatures.
• Bacterial infections: Such as pneumonia, urinary infections, throat infections, and ear infections.
• Serious infections: Including bloodstream infection (sepsis) and meningitis, which need urgent care.
• Heat-related illness: Overheating from a very hot environment.
• Inflammatory conditions and certain medications or vaccines: Less common causes of raised temperature.

Associated Symptoms

A high fever is often accompanied by other symptoms that help point to the cause:

• Chills, shivering, and sweating
• Headache and body aches
• Cough, sore throat, or runny nose with respiratory infections
• Fatigue and loss of appetite
• Nausea, vomiting, or diarrhea
• Warning features such as a stiff neck, confusion, a rash that does not fade with pressure, or breathing difficulty

Diagnosis & Evaluation

A clinician measures the temperature and assesses overall wellbeing, then looks for the source of infection. Evaluation depends on age and symptoms.

• Examination: Checking the throat, ears, chest, abdomen, and skin.
• Urine and blood tests: To look for infection and assess severity.
• Chest X-ray: If a chest infection is suspected.
• Further tests: Such as a lumbar puncture if meningitis is a concern, or swabs for specific viruses.

Treatment & Management

Treatment aims to find and treat the cause while keeping the person comfortable.

• Fluids and rest: Drinking plenty of fluids prevents dehydration; rest supports recovery.
• Fever-reducing medicine: Paracetamol (acetaminophen) or ibuprofen, at the correct dose for age and weight, can ease discomfort. Do not give aspirin to children.
• Keeping cool: Light clothing and a comfortable room temperature; avoid cold baths or sponging that cause shivering.
• Treating the cause: Antibiotics are used only for bacterial infections, guided by a doctor, and are not helpful for viral illnesses.

There is no need to try to bring the temperature down to normal; the aim is comfort, not a particular number on the thermometer. Keep checking how the person looks and responds, as a child who is alert and drinking is usually more reassuring than the height of the fever alone.

Self-Care & Prevention

Many of the infections that cause high fevers can be reduced with everyday measures, and good self-care helps recovery:

• Wash hands regularly: Frequent handwashing limits the spread of viruses and bacteria.
• Keep up with vaccinations: Routine and seasonal vaccines protect against several causes of serious fever.
• Rest and hydrate: During a fever, rest and plenty of fluids support the body's recovery and prevent dehydration.
• Dress lightly: Light clothing and a comfortable room temperature help the body shed excess heat; avoid wrapping up tightly.
• Use medicine sensibly: Paracetamol or ibuprofen at the correct dose can ease discomfort; never give aspirin to children.
• Avoid close contact when unwell: Staying home when feverish helps protect others.

Always monitor how the person looks and behaves, since this matters more than the exact temperature.

When to See a Doctor

Seek emergency care immediately for a high fever with any of these:

• A stiff neck, severe headache, confusion, or unusual drowsiness
• A rash that does not fade when pressed
• Difficulty breathing, a blue tinge to the lips, or chest pain
• A seizure, or being very hard to wake
• Any fever in a baby under 3 months, or signs of dehydration

Also see a doctor for a fever that lasts more than a few days, keeps returning, or comes with worsening symptoms.

Related Topics

Frequently Asked Questions

References

1. Mayo Clinic. Fever — Symptoms and causes.
2. MedlinePlus, U.S. National Library of Medicine. Fever.
3. Centers for Disease Control and Prevention (CDC). Fever and illness.