Introduction Temperature is a measure of the average kinetic energy of a collection of particles. Body temperature is maintained in a narrow range that permits biochemical enzymatic reactions necessary for homeostasis to occur. Although normal body temperature is often considered to be 37°C, this is an oversimplification. Body temperature actually fluctuates over the course of the day (with an early morning nadir and evening peak) and also varies based on age (lower in older individuals), gender (lower in males), activity level, and site at which it is measured. Mean rectal temperatures are typically in the range of 36.7 to 37.5°C, and mean axillary temperatures are 35.5 to 37°C.