Quick Facts

  • Elevation of normal body temperature.

  • Body temperature of 100.4 degrees Fahrenheit or higher

  • A symptom of another condition.

Fever Doctors

Mary Ann King, DO

Mary Ann King, DO


Roy Thomas, MD

Roy Thomas, MD

Internal Medicine

Carlisle Livingston, MD

Carlisle Livingston, MD

Pediatrics / Internal Medicine

What is fever?

Fever is an elevation of normal body temperature. Normal Temperature is 98.6. This is an average, as some people have higher and lower temperatures. Temperatures can also change throughout the day. Fever is a temperature of 100.4 degrees Fahrenheit or higher.

Measuring temperature

Temperature is more accurate if taken in core sites, which are oral and rectal. There are other ways to measure including under the arm, forehead, and in the ear. These methods are less accurate.

Causes of fever

Fever is a symptom of something and not a disease by itself. There are many causes of fever. These include:

  • Infections including viral, bacterial, and fungal infections
  • Autoimmune conditions
  • Certain medications
  • Cancers
  • Environmental conditions such as heat stroke

Treatment for fever

Symptoms improve with medications like acetaminophen (Tylenol) and ibuprofen (Motrin and Advil). The treatment depends on treating the underlying cause.

Fevers by Age


Fever is a medical emergency in children less than 29 days of age, and very urgent under 2 months. We recommend going to the closest ER for evaluation if you cannot immediately be seen by your doctor. These babies are at risk for many infections. This includes some infections exposed to during birth.


Fever in children is usually due to an infection. Many of which will resolve on their own, such as viruses. Some infections, like streptococcus (strep throat) and pneumonia, are treated with antibiotics. It is rare, but some childhood arthritis and cancers can have associated fevers.


As with children, infections are the most common cause of fever in adults. Adults are a more likely to have prolonged fevers. These may be atypical infections, autoimmune disease, and some cancers.


Pregnant mother are at risk for infections the same as other adults. Mother can have fevers during labor and delivery. Evaluation is done in these situations because of risk to baby and mom.


Fevers in older adults required evaluation. This is due to decreasing immune system function with some disease. Older adults tend to have fewer symptoms and need more evaluation.

Fever FAQs

Can fevers cause seizures?

In young children, fevers that rise rapidly can trigger a febrile seizure. It can also trigger increased seizures in people with a known seizure disorder.

What is a dangerous fever?

A temperature of greater than 104 is severe and warrants evaluation. The main consideration for evaluation is other symptoms. Fever of less than 104 with severe symptoms needs evaluation. These symptoms include but are not limited to headache, confusion, and lethargy.

What causes fever?

It is a response of the body that starts in the brain with chemical signals. The body is responding to some stimulus to do this, such as infection.

How long does fever last?

It varies with the underlying cause. It can last from a few days to weeks.

Can fever cause dehydration?

Fever causes the blood vessels in the skin to dilate leading to more loss of fluid. Fevers can also lead to faster breathing. Both of these can lead to dehydration.