The normal range of sublingual temperature is 36.3-37.2°C, which is measured with a mercury thermometer in a hot nest under the tongue. The measurement method is to place the thermometer under the tongue for 3 minutes, if there is smoking, cold compress on the face or just after eating, it needs to be measured after half an hour, otherwise the measurement value will have a large error. In addition, the sublingual temperature is closer to the internal temperature of the body than the armpit temperature, but the sublingual temperature measurement method is not as widely applicable to the population as the armpit. The following groups of people are not suitable for sublingual temperature measurement, including comatose patients, patients with mental illness, infants and children, who may bite the thermometer due to lack of autonomy, resulting in damage to the oral mucosa, mercury poisoning, etc. Those who have oral and nasal surgery, oral diseases, and respiratory difficulties should also not measure sublingual temperature.