How to Measure a Fever in Children
Monitoring a child’s temperature is one of the first and most important steps when managing a fever. This guide will walk you through common methods for checking a child’s temperature, age-specific recommendations, and when it may be time to consult a healthcare provider.
Choosing the Right Thermometer
Digital thermometers are widely recommended because they are fast, accurate, affordable, and easy to use. They can be used in several ways — under the arm (axillary), by mouth (oral), or rectally — depending on the age of the child.
Important: Each thermometer should only be used for one method. For example, a thermometer used for rectal readings should not also be used orally.
Babies Under 3 Months Old
For newborns and very young infants, the rectal method is the most reliable. If your baby is under 3 months and has a temperature of 38.0°C (100.4°F) or higher, contact your doctor immediately. At this age, a fever may be a sign of a more serious condition.
How to Take a Rectal Temperature:
Wash and rinse the thermometer with cool water.
Apply a small amount of petroleum jelly to the tip.
Lay your baby on their back with legs bent, or place them on their belly.
Gently insert the thermometer about ½ to 1 inch into the rectum.
Hold until it beeps, then read the temperature.
Children Under 4 Years Old
Toddlers and preschool-aged children may not tolerate rectal thermometers well. The underarm method (axillary) is a simpler, although slightly less accurate, option.
How to Take an Underarm Temperature:
Remove the child’s shirt and dry the underarm.
Place the thermometer tip in the center of the armpit.
Hold the arm snugly against the body.
Wait until the thermometer beeps, then check the reading.
Children Ages 4 and Up
Older children can usually hold a thermometer in their mouth long enough to get an accurate oral temperature reading.
How to Take an Oral Temperature:
Rinse the thermometer with cool water before use.
Place the tip under the child’s tongue toward the back of the mouth.
Hold in place until the thermometer beeps, then remove to read.
What Temperature Counts as a Fever?
Body temperature naturally fluctuates during the day, but the following thresholds are generally considered signs of a fever:
Oral: Above 37.5°C (99.5°F)
Rectal or Ear: Above 38.0°C (100.4°F)
Underarm: Above 37.3°C (99.1°F)
If your child’s temperature is 38.3°C (101°F) or higher and lasts longer than 24 hours, contact your healthcare provider.
When to Call a Doctor
Fevers are often a sign that the body is fighting off a minor illness such as a cold, flu, or ear infection. In most cases, a fever will resolve on its own within a couple of days. However, seek medical advice if:
Your baby is under 3 months and has a fever.
The fever lasts more than 3 days.
New or worsening symptoms appear.
Medpac Children’s Pain & Fever Relief (Ages 2–11)
Medpac offers an acetaminophen-based liquid suspension formulated for children ages 2 to 11 to help reduce fever and relieve mild to moderate pain. Always read the label for dosing instructions and consult your healthcare provider if you’re unsure about how much to give your child.
Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak to your doctor or pharmacist about any health concerns.
