A digital thermometer is the standard instrument used for measuring body temperature in adults. These devices rely on internal heat sensors, known as thermistors, to quickly detect temperature changes and translate that information into a precise digital reading within seconds. This electronic method offers significant advantages in convenience and speed compared to older glass thermometers. The clear digital display also eliminates the potential for human error associated with interpreting mercury levels, making it a reliable tool for at-home health monitoring.
Preparation and Setup
Before initiating any temperature measurement, the digital thermometer must be prepared to ensure both hygiene and accuracy. The probe should be cleaned with a disinfectant, such as a wipe or a cotton ball soaked in at least 60% isopropyl alcohol. After disinfecting, allow the probe to air-dry completely or rinse it with cool water, taking care not to wet the electronic display components.
Once clean, the device should be powered on to check the battery life and display function. Most digital thermometers will briefly show all segments of the screen or the last recorded reading before displaying the ready-to-measure symbol. Always ensure the thermometer has been reset and cleared of its previous reading before placing it for a new measurement.
Standard Measurement Methods
The two most common methods for using a digital thermometer in adults are the oral (sublingual) and the axillary (underarm) routes, which offer a balance of convenience and reliability. To take an oral temperature, the tip of the thermometer’s probe must be placed deep under the tongue, resting in one of the heat pockets located on either side of the mouth. The adult should then close their lips around the device, avoiding biting down or moving the probe, and breathe normally through the nose to prevent cool air from entering the mouth and skewing the result.
Wait at least 15 to 30 minutes after eating, drinking, or smoking before taking an oral temperature, as these activities temporarily alter the mouth lining temperature. The thermometer must remain in place until the device signals completion, usually with a series of beeps or a flashing display.
For the axillary method, the thermometer tip is placed directly into the center of the armpit, ensuring the probe touches only bare skin and not clothing. The arm must then be held tightly down against the side of the body, trapping the thermometer to guarantee continuous contact and reduce ambient air interference. Because the armpit is an external skin temperature reading, the final result will be less reflective of the body’s internal core temperature. This method requires the user to hold the thermometer firmly in place until the signal indicates the reading is complete.
Interpreting Temperature Readings
After the thermometer beeps, the number displayed represents the body temperature at that specific measurement site. The average normal oral temperature for a healthy adult is approximately 98.6°F (37°C), with an accepted range extending from about 97.0°F to 99.0°F (36.1°C to 37.2°C). A reading taken in the mouth that reaches 100.0°F (37.8°C) or higher is considered to indicate a fever.
The reading will vary based on the location where the temperature was taken. An axillary (underarm) temperature is consistently lower than an oral reading because the skin surface is cooler. Typically, an axillary temperature will measure 0.5°F to 1.0°F (0.3°C to 0.6°C) below the corresponding oral temperature. Therefore, a reading of 99.0°F (37.2°C) or above in the armpit is considered a fever, reflecting the necessary adjustment for the site variation.
Maintaining Accuracy and Care
Proper maintenance of a digital thermometer is important for preserving its accuracy and longevity. After each use, the thermometer must be cleaned and disinfected to prevent the spread of germs. Use a cotton pad dampened with rubbing alcohol to wipe the probe and the body of the device, allowing it to air-dry completely before storage. Avoid submerging the electronic components in water or using hot water for cleaning, as this can damage the sensor and internal circuitry.
Storing the device in its protective case, away from extreme temperatures and moisture, helps safeguard the electronics. Results can be skewed by factors such as recent exercise, which temporarily raises body temperature, or the use of certain medications like acetaminophen or ibuprofen. Always check the battery when the display appears dim or the device takes an unusually long time to register a final temperature, as a weak battery is a common cause of inaccurate readings.