How to Take a Baby's Temperature

By Susan Revermann
Thinkstock/Comstock/Getty Images

Your baby’s temperature is regulated by a tiny part of the brain called the hypothalamus and you get to control how to take her temperature when you suspect she is running hot. Depending on your little one’s age, you can get a temperature reading in a few ways. Once you know how warm she is, you need to decide how to react to the problem.

Step 1

Know the correct thermometer and testing place for your baby. For newborns to 3 months, use a digital thermometer to take a rectal temperature reading. For babies and toddlers who are between 3 months and 4 years, you can take a rectal temperature reading for the most accurate reading, or you can take an armpit reading. Armpit readings are the least accurate choice, but can be used, if needed. A digital pacifier thermometer or temporal artery thermometer can also be used for this age group. Wait until your baby is at least 6 months old to use a digital ear thermometer. After 4 years of age, you can switch to a digital thermometer under the tongue.

Step 2

Grab the thermometer and place a plastic protective sheath over the end, if you have them handy. These are disposable and help keep germs in check. If you’re using a thermometer for rectal readings, label this one and have a separate thermometer for oral or armpit readings.

Step 3

Insert the thermometer in the proper location. For a rectal reading, turn the digital thermometer on and lubricate the end with petroleum jelly for easier use. Position your baby on his back, lift his legs and insert the thermometer 1/2 to 1 inch into the rectum. Hold his legs in place with one hand so he doesn’t wiggle around too much and steady the thermometer between your fingers of the other hand. Remove the thermometer gently when it has its reading. For an armpit reading, turn the thermometer on and place it under his armpit against the skin. Gently press his arm down until the reading is ready. The temporal artery thermometer is run across the side of the forehead. When you want to take an ear reading, follow the product instructions. Each model can vary. Generally, you will turn the device on, hold the tip in his ear and wait for the reading.

Step 4

Read the temperature reading and then turn off the thermometer. Throw the protective sheath away in the garbage, if you used one.

Step 5

Clean the tip of the thermometer after use with a cotton ball and rubbing alcohol or soapy warm water and a washcloth. Store it in a clean, dry place, out of children’s reach.