A person has a fever if their body temperature rises above the normal range of 98–100°F (36–37°C). It is a common sign of an infection.
As a person’s body temperature increases, they may feel cold until it levels off and stops rising. People describe this as “chills.”
Eating, exercise, sleeping, the time of day, and individual factors can also affect temperature.
When an infection occurs, the immune system will launch an attack to try to remove the cause. A high body temperature is a normal part of this reaction.
A fever will usually resolve on its own. However, if body temperature rises too high, it may be a symptom of a severe infection that needs medical treatment. In this case, a doctor may recommend medication to reduce it.
Read on to learn more about the symptoms of a fever, as well as some causes and treatment options.
Symptoms of fever
The symptoms of fever can include:
- feeling unwell
- feeling hot and sweaty
- shivering or shaking
- chattering teeth
- flushed face.
Infection is usually the cause of fever
The cause of fever is usually an infection of some kind. This could include:
- diseases caused by viruses – such as colds, flu, COVID-19 or other upper respiratory tract infections
- diseases caused by bacteria – such as tonsillitis, pneumonia or urinary tract infections
- some chronic illnesses – such as rheumatoid arthritis and ulcerative colitis can cause fevers that last for longer periods
- some tropical diseases – such as malaria, which can cause bouts of recurring fever or typhoid fever
- heat stroke – which includes fever (without sweating) as one of its symptoms
- drugs – some people may be susceptible to fever as a side effect of particular drugs.
What is the best way to measure body temperature?
The best way to measure body temperature is using a thermometer inserted orally, rectally, axillary (under the arm), or by using a special instrument commonly sold in stores that is inserted in the ear and measures the temperature of the eardrum.
Can a fever be treated at home?
If your fever is mild (less than 101°F), then no medical treatment is required. Simply make sure that you drink plenty of fluids (not alcohol) – and get plenty of rest.
For higher temperatures, there are many effective ways to getting your fever under control. The most common way includes medications such as aspirin, acetaminophen and ibuprofen.
If you have a child under age 17 who has a fever, DO NOT give the child aspirin. Aspirin in children may cause Reye’s syndrome, a sometime fatal illness. Taking a lukewarm bath (around 98°F) may also help bring the body’s temperature down.
When is a fever cause for concern?
If any of the following situations apply, call a doctor as soon as possible:
- A fever accompanied by a stiff neck, confusion or irritability.
- A fever remaining above 103°F (39.5°C) longer than two hours after home treatment.
- A fever lasting longer than two days.
- High fever accompanied by rash.
- Photophobia (irritated by light).
- Dehydration (less amount of urine, sunken eyes, no tears).
Any fever in an adult that goes above 105°F (or 40.5°C) and does not come down with treatment is a life-threatening medical emergency.
Self-treatment suggestions for fever
Suggestions to treat fever include:
- Take paracetamol or ibuprofen in appropriate doses to help bring your temperature down.
- Drink plenty of fluids, particularly water.
- Avoid alcohol, tea and coffee as these drinks can cause slight dehydration.
- Sponge exposed skin with tepid water. To boost the cooling effect of evaporation, you could try standing in front of a fan.
- Avoid taking cold baths or showers. Skin reacts to the cold by constricting its blood vessels, which will trap body heat. The cold may also cause shivering, which can generate more heat.
- Make sure you have plenty of rest, including bed rest.