Age guidelines

The best type of thermometer or the best place to insert it, in some cases, depends on your child's age.

• Birth to 3 months. Use a regular digital thermometer to take a rectal temperature. New research suggests that a temporal artery thermometer also might provide accurate readings in newborns.
• 3 months to 4 years. In this age range, you can use a digital thermometer to take a rectal or an armpit temperature. Or you can use a temporal artery thermometer. Wait until your baby is at least 6 months old to use a digital ear thermometer. If you use another type of thermometer to take a young child's temperature and you question the results, take a rectal temperature.
• 4 years and older. By age 4, most kids can hold a digital thermometer under the tongue for the short time it takes to get an oral temperature reading. You also can use a digital thermometer to take an armpit temperature, a temporal artery thermometer or a digital ear thermometer.