A device for determining normalized body temperature comprising a temperature sensor, an input device, a processor configured with a temperature-normalizing algorithm, memory, and an output device is described herein. Also disclosed is a method for determining physiologically significant changes in body temperature comprising providing raw body temperature of a subject, providing data for a temperature-normalizing algorithm, quantitatively normalizing the raw body temperature with an algorithm comprising an equation containing at least one body temperature-affecting variable to obtain a normalized body temperature, and comparing the normalized body temperature to a second temperature.