Nov 28, 2022 12:00 AM

Author: University of Utah Health Communications


Información en español

Do you find yourself placing the back of your hand on your forehead to gauge your temperature? A high temperature is an indicator that you might be falling ill. Learning how to take your temperature and which thermometer to use are important parts of maintaining your health.

Your temperature changes throughout the day

If you are monitoring your temperature, be sure to check it around the same time each day. It’s important to be consistent because your temperature fluctuates hour by hour.

The average body temperature is 98.6 degrees Fahrenheit but varies from 97.7 to 99.5 degrees. Fluctuations are due to changes in hormonal activity over the course of the day, your environment, and physical activity. For instance, you may have a lower temperature in the morning after sleeping in a cold room, and a higher temperature after exercising or doing housework.

Choose the appropriate thermometer

Just as some factors determine our body temperature, other factors affect your temperature reading. For example, your oral temperature can change after being outside, drinking coffee, or eating ice cream.

These tips can help you get the best readings from the most frequently used home thermometers.

Ear thermometers use infrared light to measure the temperature inside the ear canal. This method is recommended for ages 6 months and older. While ear thermometers are relatively easy to use, there are certain things to watch for, such as:

  • Placement in the ear canal is important. Make sure to get into the ear canal far enough.
  • The ear needs to be clean. Too much ear wax can interfere with readings.

Temporal (forehead) thermometers have an infrared scanner that records the temperature of the temporal artery at the forehead. They measure temperature quickly and can be used for all ages.

  • Place the sensor on the center of the forehead and slide toward the top of the ear until you get to the hairline.
  • Read the instructions for “no-touch” models to find out how close they should be placed to the forehead.

Oral thermometers measure the temperature in the mouth. They are not recommended until a child is 4 years or older. While they are easy to use and inexpensive, they are somewhat less reliable.

  • Avoid consuming hot or cold foods prior to taking your temperature.
  • Clean with soap and warm water or rubbing alcohol before use.
  • Place under the tongue and close your mouth for one minute before removing.

Rectal thermometers are recommended by the American Academy of Pediatrics for babies and children up to the age of 3 years. Studies have shown this method is the most accurate for temperature screening.

  • Lubricate the tip of the thermometer with petroleum jelly.
  • Insert the thermometer half an inch to one inch into the rectum.
  • Hold the thermometer in place until it signals that it’s done.

If you don’t feel comfortable using a rectal thermometer, you can put a digital thermometer in the armpit of a child. If the thermometer shows a fever (100.4 degrees or higher), the temperature should be rechecked with a more accurate method.

What is considered a fever and when to get help

A fever isn’t always a cause for concern—it’s the body’s natural response to fight infection. A fever is considered 100.4 degrees or higher. But there are times that you should be seen by a doctor, such as:

  • Children younger than 3 months old who have a temperature of 100.4 or higher.
  • Children ages 3 to 6 months who have a temperature 102 or higher.
  • Children ages 6 to 24 months who have a temperature higher than 102 that lasts longer than one day.
  • If your child has a fever for more than five days and develops other concerning symptoms.
  • Adults that have a temperature of 103 or greater and are experiencing other signs or symptoms.

fever temperature thermometer

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