If your child is ill or feels warm to touch, it is a good idea to take their temperature to check for a fever—especially before they go to school, daycare, sports, or other activities. But with all of the different methods and types of thermometers available, it may be difficult to know which is best to use and when. Use the following guidelines to understand how to take your child’s temperature safely and accurately as well as when to use each method, categorized by age.

Infants younger than 3 months old with a rectal temperature of 100.4℉ (38℃) and higher could indicate a dangerous infection and is considered an emergency. These infants require immediate medical attention even if they appear well and show no other signs of illness.

When your child is sick and has a fever, it can be a parent’s first instinct to try to immediately treat and bring down the fever as well as call the pediatrician to be seen right away. While this reaction is understandable—we all just want our kids to be healthy and safe—it may not be necessary. Learning the basics of fevers, including what causes them and what to look out for, can lessen parents’ fears and anxieties and help them confidently care for their children when sick.