Definition

Normal body temperature varies by person, age, activity, and time of day. The average normal body temperature is generally accepted as 98.6°F (37°C). Some studies have shown that the "normal" body temperature can have a wide range, from 97°F (36.1°C) to 99°F (37.2°C).

A temperature over 100.4°F (38°C) most often means you have a fever caused by an infection or illness.

Body temperature normally changes throughout the day and in adults, it is lowest in the early morning.

Alternative Names

Normal body temperature; Temperature - normal

References

Blum FC, Biros MH. Fever in the adult patient. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 8.

Hall JE, Hall ME. Body temperature regulation and fever. In: Hall JE, Hall ME, eds. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 74.

Sajadi MM, Romanovsky AA. Temperature regulation and the pathogenesis of fever. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 55.