Fever

What is a fever?

A fever is a body temperature that is higher than normal. It usually means there is an abnormal process occurring in the body. Exercise, hot weather, and common childhood immunizations can also make body temperature rise.

What causes a fever?

A fever is not an illness by itself. Rather it is a symptom that something is not right within the body. A fever does not tell you what is causing it, or even that a disease is present. It may be a bacterial or viral infection. Or, it could be a reaction from an allergy to food or medicine. Becoming overheated at play or in the sun can also result in fever.

What are the symptoms of a fever?

Normal body temperature ranges from 97.5°F to 98.9°F (36.4°C to 37.2°C). It tends to be lower in the morning and higher in the evening. Most healthcare providers consider a fever to be 100.4°F (38°C) or higher. High fevers may bring on seizures or confusion in children. It’s not how high the temperature is, but how fast the temperature goes up that causes a seizure.

A fever has other symptoms besides a higher-than-normal temperature. These are especially important when caring for babies, young children, and disabled people. These groups may not be able to express how they feel. Signs that mean fever include:

  • Flushed face
  • Hot, dry skin
  • Low output of urine, or dark urine
  • Not interested in eating
  • Constipation or diarrhea
  • Vomiting
  • Headache
  • Aching all over
  • Nausea

How is a fever diagnosed?

The best way to diagnose a fever is to take a temperature with a thermometer. There are several types of thermometers, including the following:

  • Digital thermometer (oral, rectal, or under the armpit)
  • Tympanic (ear) thermometer (not recommended in babies younger than 6 months of age)
  • Temporal artery (temperature taken across the forehead area)

Taking a temperature rectally is the most accurate method in children under 3 years of age. In older children and adults, take the temperature under the armpit or in the mouth. Talk with your healthcare provider about the best way to take your temperature.

Most thermometers today are digital, but there are some glass thermometers containing mercury still in use. Mercury is toxic substance and is dangerous to humans and the environment. Because glass thermometers can break, they should be disposed of properly in accordance with local, state, and federal laws. For information on how to safely dispose of a mercury thermometer, contact your local health department, waste disposal authority, or fire department.