Taking body temperature is usually done for at least 5 minutes if it is measured with a mercury thermometer. Because the mercury thermometer is to use the characteristics of thermal expansion and contraction to measure body temperature, so to give enough time to expand. However, generally speaking, it is not necessary to measure for more than 10 minutes, because once the mercury expands to a level comparable to the body temperature, the measurement will not continue to rise for a longer period of time. Therefore, the mercury thermometer measurement of about 5 minutes is sufficient. Whether it is measuring the axillary temperature or oral temperature or rectal temperature, you can use a mercury thermometer to measure, it is necessary to take the correct measurement method and measure long enough to get an accurate body temperature count. If it is measured with an electronic thermometer, different brands of electronic thermometers may have different measurement times, generally speaking, about 1-3 minutes to complete the measurement, after which the machine will automatically sound a beep, so that the measurement can be ended.