A medical thermometer is a device used to measure a person's body temperature. It helps determine if someone has a fever, which can indicate an illness. There are different types of thermometers, including digital, infrared, and glass thermometers. Digital thermometers are popular because they provide quick and accurate readings, while infrared thermometers can measure temperature without direct contact. Using a medical thermometer is simple. You place it under the tongue, in the armpit, or in the rectum, depending on the type. After a few seconds, the thermometer displays the temperature, helping caregivers and doctors assess a patient's health.