The definition of fever is an elevation in body temperature. Technically, any body temperature above the normal oral measurement of 98.6 F (37 C) or the normal rectal temperature of 99 F (37.2 C) is considered to be elevated. However, these are averages, and one’s normal body temperature may actually be 1 F (0.6 C) or more above or below the average of 98.6 F. Body temperature can also vary up to 1 F (0.6 C) throughout the day.
Fever is not considered medically significant until body temperature is above 100.4 F (38 C). Anything above normal but below 100.4 F (38 C) is considered a low-grade fever. Fever serves as one of the body’s natural defenses against bacteria and viruses that cannot live at a higher temperatures. For that reason, low-grade fevers should normally go untreated, unless accompanied by troubling symptoms.
Also, the body’s defense mechanisms seem to work more efficiently at a higher temperature. Fever is just one part of an illness, many times no more important than the presence of other symptoms such ascough, sore throat, sinus congestion,fatigue, joint pains or aches, chills, nausea, etc.