FEVER

The temperature of the body is controlled by a section of the brain that acts like a "thermostat." Normal body temperature varies depending on the individual, the time of day, and other factors such as strenuous exercise, response to medications, or even level of excitement. Temperature is measured using a thermometer. The average body temperature is 98.6 degrees Fahrenheit or 37 degrees Centigrade orally. A normal temperature can range from 97 degrees Fahrenheit to 99 degrees Fahrenheit (36.1 degrees Centigrade to 37.2 degrees Centigrade).

Fever is defined as an elevation of body temperature one or more degrees higher than what is conventionally defined as normal. Fever occurs when the body's thermostat is reset at a higher level.

Body temperature of 100 degrees Fahrenheit (37.7 degrees Centigrade) to 102 degrees Fahrenheit (38.8 degrees Centigrade) orally is usually described as a low-grade fever. Temperature 103 degrees Fahrenheit (39.4 Centigrade) orally or higher is said to be a high-grade fever. Generally, oral temperatures of 102 degrees Fahrenheit (38.8 degrees Centigrade) or higher are fevers that may be more serious. Fevers of undetermined origin are unexplained fevers of 100 degrees Fahrenheit (37.7 degrees Centigrade) or higher orally lasting for more than 3 weeks.

When the temperature-control center of the brain perceives a threat, it sends messages to muscles and blood vessels in the skin. The muscles begin to shake repeatedly, or shiver, causing heat production. Chills can be constant for up to one hour or they can come and go. The messages to blood vessels in the skin cause them to constrict to retain more heat. These two actions raise body temperature.

A fever is a symptom, not a disease. A fever can be a sign that the body is fighting an infection. Not all fevers mean a person has a serious illness or needs an antibiotic. A fever can also occur as a symptom of other conditions such as dehydration, certain thyroid disorders, autoimmune disorders, or even cancer.

Most healthy children and adults can tolerate a low or moderate fever for a few days at home without problems. Some other symptoms that may occur when you have a fever are muscle aches, headache, lack of appetite, feeling chilled or sweaty, or generally not feeling well. Often the importance of a fever can only be determined when other associated symptoms are evaluated.

Fever that should be reported to your provider includes:

For children --

An infant younger than 3 months with any fever
An infant between 3 months and 1 year with a fever that has lasted more than 24 hours
A fever that remains above 103 degrees Fahrenheit (39.4 degrees Centigrade) after an hour or two of home treatment
A fever that continues for more than 2 days
A fever along with unexplained crying, sleeping more than usual or not as alert as usual

Other symptoms of concern with a fever are: repeated vomiting, being too ill to drink or refusing to drink, stomachache, severe headache, a rash, or behavior that is different than usual.

For adults --

A fever of 103 degrees Fahrenheit (39.4 Centigrade) or higher
A fever of 101 degrees Fahrenheit (38.3 Centigrade) or higher that lasts longer than 3 days
A fever associated with any of the following new or worsening symptoms:

shortness of breath
severe or persistent headache
significant stiff neck and pain when bending the head forward
sensitivity to bright lights
mental confusion or drowsiness
seizure or convulsion
moderate to severe pain
redness, swelling, tenderness or other signs of local infection

A fever of 100.5 degrees Fahrenheit (39.1 degrees Centigrade) or greater OR a temperature of 100 degrees Fahrenheit (37.7 Centigrade) for 3 days when pregnant

It is helpful to keep a temperature log when you have a fever. Record answers to these questions:

When did the fever begin?
What was the highest reading?
Is the fever constant, or does it go away and come back?
Are any other symptoms present?
Does the fever respond to temperature-reducing medication, such as acetaminophen or ibuprofen?
Any other medications that are taken?
Any recent sickness or injury?
Any recent medical test or surgery?
Exposure to anyone else who may have been ill?

These questions will help your healthcare provider determine the reason for fever and how best to deal with it.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIL File SYMP4908.RF2 VRS# 4908 Data Version 7.0