Body temperature represents the balance between heat produced by metabolism, muscular activity, and other factors and heat lost through the skin, lungs, and body wastes. A stable temperature pattern promotes proper function of cells, tissues, and organs; a change in this pattern usually signals the onset of illness.

Temperature can be measured with an electronic digital, chemical-dot, or tympanic thermometer. Oral temperature in adults normally ranges from 97° to 99.5°F (36.1° to 37.5°C); rectal temperature, the most accurate reading, is usually 1°F (0.6°C) higher; axillary temperature, the least accurate, reads 1° to 2°F (0.6° to 1.1°C) lower; and tympanic temperature reads 0.5° to 1° (0.3° to 0.6°) higher.¹

Temperature normally fluctuates with rest and activity. Lowest readings typically occur between 4 and 5 a.m.; the highest readings occur between 4 and 8 p.m. Other factors also influence temperature, including gender, age, emotional conditions, and environment. Keep the following principles in mind: Women normally have higher temperatures than men, especially during ovulation. Normal temperature is highest in neonates and lowest in the elderly. Heightened emotions raise temperature; depressed emotions lower it. A hot external environment can raise temperature; a cold environment lowers it.