Health Topic

Fever

Are you running a temperature? Learn what can cause a fever and how to know when a fever can be dangerous.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Pyrexia

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Fever

A fever is a body temperature that is higher than normal. A normal temperature can vary from person to person, but it is usually around 98.6 °F (37 °C). A fever is not a disease. It is usually a sign that your body is trying to fight an illness or infection.

Infections cause most fevers. You get a fever because your body is trying to kill the virus or bacteria that caused the infection. Most of those bacteria and viruses do well when your body is at your normal temperature. But if you have a fever, it is harder for them to survive. Fever also activates your body's immune system.

Other causes of fevers include:

  • Medicines, including some antibiotics, blood pressure medicines, and anti-seizure medicines
  • Heat illness
  • Cancers
  • Autoimmune diseases
  • Some childhood vaccines

Treatment depends on the cause of your fever. If the fever is very high, your health care provider may recommend taking an over-the-counter medicine such as acetaminophen or ibuprofen. Adults can also take aspirin, but children with fevers should not take aspirin. It is also important to drink enough liquids, to prevent dehydration.

It sits within Infections and Symptoms.

The lead U.S. institute for this subject is the National Institute of Allergy and Infectious Diseases.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Fever

2,318 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

Start Here

Diagnosis and Tests

Treatments and Therapies

Genetics

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Fever. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Fever, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.