Is a mercury thermometer accurate for taking children’s temperature?

Mercury-in-glass thermometers offer high measurement accuracy; however, they pose certain safety hazards during use and are unsuitable for young, active children. When used correctly, their readings are reliable—but if a child moves excessively during measurement, results may be inaccurate. If a child experiences persistent high fever or appears lethargy, prompt medical evaluation is essential.

Mercury-in-glass thermometers detect temperature changes based on the thermal expansion and contraction of mercury, providing stable and consistent readings—making them a traditional standard in temperature measurement. However, their glass construction renders them fragile; if broken, mercury can vaporize, posing a risk of mercury poisoning. Infants and toddlers often cry, squirm, or fail to hold the thermometer securely under the arm, leading to falsely low readings. Axillary measurement requires the thermometer to remain firmly in place for 5–10 minutes; insufficient time will compromise accuracy.

In clinical practice, electronic thermometers are strongly recommended for children due to their ease of use and absence of mercury leakage risks. If using a mercury thermometer, close supervision of the child is mandatory to prevent breakage. Should breakage occur, avoid direct skin contact with mercury droplets; ensure adequate room ventilation and carefully collect all scattered mercury. Never place a mercury thermometer in the mouth for oral measurement, as biting it may cause injury or mercury exposure.

For routine temperature monitoring, axillary measurement is preferred. Before measuring, ensure the armpit is dry by wiping away sweat. Avoid taking temperature immediately after physical activity or consumption of hot beverages; instead, allow the child to rest briefly first—this yields a more accurate and physiologically representative reading.