Fever is defined as a body temperature that is 1 or more degrees higher than normal. Normal body temperature varies from person to person, by age, by the time of day, and by the part of the body where it is measured. Other factors such as strenuous exercise, medicines, or even excitement can also affect body temperature.

Your temperature can be measured with a thermometer in the mouth, ear, or rectum, or under the armpit. When the temperature is measured in the mouth (orally):

• A temperature between 97 to 99 degrees Fahrenheit (F) is considered normal.
• A temperature of 100 to 102 degrees F is usually called a low-grade fever.
• A temperature of 103 degrees F or higher is called a high-grade fever.

Generally, oral temperatures of 102 degrees F or higher are fevers that may be more serious.  Temperatures measured in the ear or rectum are higher than oral temperatures by one half to 1 degree F, and temperatures measured in the armpit are lower by one half to 1 degree F.  A fever is a symptom, not a disease. Fever can be a sign that the body is fighting an infection. Fever may occur with viral or bacterial infections such as ear infections, the flu, severe colds, sore throats, pneumonia, stomach viruses, or urinary tract infections. A fever can also be a symptom of other medical problems such as dehydration, a thyroid disorder, or an autoimmune problem.