Is it still accurate if the thermometer is held in place for 15 minutes?

Generally speaking, whether a thermometer is still accurate after being held for 15 minutes mainly depends on whether the thermometer was placed correctly and whether there were any external factors interfering. If the thermometer was placed correctly and there were no external interferences, the reading usually is accurate; however, if the thermometer was placed incorrectly or there were external factors interfering, the reading may not be accurate. A detailed explanation is as follows:

Normally, the measurement time for an armpit thermometer is 5–10 minutes. However, if the measurement time is slightly longer, such as 15 minutes, as long as the thermometer was placed correctly in contact with the skin, the armpit remained tightly closed, and there were no external interferences such as drastic changes in ambient temperature, it will have little impact on the measurement result, because the mercury or temperature-sensitive material inside the thermometer maintains a relatively stable reading once it reaches body temperature.

However, if during measurement the thermometer was not held tightly or became loose, resulting in poor contact between the thermometer and the skin, even a 15-minute measurement may be inaccurate. In addition, if there was excessive perspiration during measurement, the sweat may affect the thermometer's temperature sensing and cause inaccurate results.

To avoid unnecessary errors and misunderstandings, it is recommended to read the measurement result within the specified time frame.