How many degrees above the thermometer is a fever, taking the mercury thermometer measurement in the armpit as an example. When using a mercury thermometer to measure body temperature in the armpit, the normal value of body temperature is 36.0-37.0℃, which means that a body temperature above 37.3℃ is a fever. Fever is divided into low fever, medium fever, high fever and ultra-high fever. A body temperature of 37.3-38.0℃ is low fever, 38.1-39℃ is medium fever, 39.1-41℃ is high fever, and a body temperature greater than 41℃ is ultra-high fever. Therefore, when using a mercury thermometer to measure the body temperature under the armpit, a body temperature above 37.3℃ is considered feverish. However, when measuring the anal and oral temperatures, the definition of fever is slightly different. When measuring the anal temperature, a body temperature greater than 37.8℃ is considered feverish, and when measuring the oral temperature, a body temperature greater than 37.5℃ is considered feverish.