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Alternative Names:

Elevated temperature; hyperthermia; pyrexia; temperature, elevated


Normal body temperature varies with different people, but the average is 98.6 degrees Fahrenheit (37 degrees Centigrade). If the temperature is 99 to 100 degrees Fahrenheit, suspect a fever; if it is 100 degrees Fahrenheit or above, it is a fever.


Normal body temperature varies during the day. It is generally lowest upon awakening in the morning. Food, extra clothing, excitement, and anxiety can all raise the body temperature. Strenuous exercise can temporarily raise body temperature to as high as 103 degrees Fahrenheit.

Menstrual cycles in women can also elevate temperature by 1 degree or more.

Most children have higher body temperatures than adults and seem to have more daily variation. Many infants and children develop high fevers, even with minor viral illnesses. A high fever does not directly cause brain damage. However, febrile seizures can occur in some children, and the seizure can cause injury to the child.

Fevers are described as low grade (102 degrees Fahrenheit or lower) or high grade (above 103 Fahrenheit). They are also described as spiking (the fever suddenly jumps high, then drops) or cyclic (the fever increases and decreases in a regular manner).

A heat stroke can result from too much exercise without water or salt, and temperature can rise to 106 degrees Fahrenheit.

Unexplained fevers that continue for days or weeks are referred to by doctors as fevers of undetermined origin (FUO). Most are eventually found to be caused by a hidden infection.

Common causes:

  • Viral and bacterial infections 
  • Colds or flu-like illnesses 
  • Sore throats and strep throat 
  • Earaches(otitis media) 
  • Viral gastroenteritis or bacterial gastroenteritis 
  • Acute bronchitis 
  • Infectious mononucleosis 
  • Urinary tract infections 
  • Upper respiratory infections such as tonsillitis, pharyngitis or laryngitis 
  • Dehydration 
  • Medications such as antibiotics, antihistamines, barbiturates, and drugs for high blood pressure 
  • Occasionally, more serious problems like pneumonia, appendicitis, tuberculosis(TB), and meningitis 
  • Fever can occur in infants who are overdressed in hot weather or a hot environment 
  • Collagen vascular disease, rheumatoid diseases, and autoimmune disorders 
    • Juvenile rheumatoid arthritis 
    • Lupus erythematosus 
    • Periarteritis nodosa 
    • AIDS and acute HI infection
  • Inflammatory bowel disease 
    • Regional enteritis 
    • Ulcerative colitis
  • malignant disorders (cancerous) 
    • Leukemia 
    • Neuroblastoma 
    • Hodgkin’s disease 
    • Non-Hodgkin’s lymphom


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