How long should a thermometer be held under the armpit?
Jan 13, 2025
Source: Cainiu Health
Dr. Ren Yi
Introduction
Under normal circumstances, an armpit thermometer should be held in place for more than 5 minutes. If necessary, it is recommended to follow the guidance of a physician when using it. Armpit thermometers work based on the physical principle of thermal expansion and contraction to measure body temperature. When the mercury end of the thermometer is placed under the armpit, the mercury is affected by body heat. To ensure accuracy, the thermometer should be held in place for more than 5 minutes.
Under normal circumstances, a mercury thermometer should be held under the armpit for more than 5 minutes. If necessary, it is recommended to follow the guidance of a healthcare professional. Detailed explanation is as follows:
The working principle of a mercury thermometer is based on the physical properties of thermal expansion and contraction to measure body temperature. When the mercury end of the thermometer is placed under the armpit, the mercury is affected by body heat. To ensure sufficient thermal equilibrium between the thermometer and the body, it should be held in place for more than 5 minutes, allowing the thermometer to accurately reflect the body's temperature.
When the thermometer has been held for more than 5 minutes, it will have reached thermal equilibrium with the body, and the temperature reading at this point will be closest to the actual body temperature. If the duration is too short, the thermometer may not have fully absorbed the heat from the armpit, and the mercury column may not have risen to the level corresponding to the actual body temperature. As a result, the reading may be lower than the true body temperature and fail to accurately reflect the actual body condition.
When reading the thermometer, maintain a horizontal eye level to avoid measurement errors caused by viewing angle discrepancies. After reading, shake the thermometer down below the starting scale for future use.
