How to Take Your Baby's Temperature

By JustMommies staff

There are three main methods for taking a baby's temperature: in the ear, in the armpit or rectally. Using an oral thermometer isn't recommended until a child is 4 or 5 years old (they're too squirmy before that). Rectal temperature tends to be the most accurate, but we'll look at all three methods.

Ear and Forehead Thermometers

The ear thermometer is a quick method to take a baby's temperature, but it also requires the most practice. Unless you get the sensor in the baby's ear exactly right, you won't get an accurate reading (it takes a few tries to get the hang of it). Ear thermometers can't be used on babies younger than 3 months, because their ear canals are too tiny. Once you're able to consistently get accurate readings, an ear thermometer can be very reliable.
The forehead scanning thermometers are digital and fairly easy to use on babies, but can be less accurate than the ear thermometers. Forehead thermometer measurements are comparable to an oral temperature from a quality thermometer that you might use for an older child, but are more manageable to use for a baby.

Armpit Temperature

This is a simple method that can be done when you're breastfeeding, or any time when your baby is calm and lying still. Undress him and place the tip of a digital thermometer in his armpit. Hold it in place with his arm until you can get a reading. While this is the simplest method, it's also the least accurate. External temperature can be up to 2 degrees cooler than an internal rectal reading.

Rectal Temperature

This gives the most accurate reading. Clean the thermometer first with soap and water, and coat the tip with a little bit of petroleum jelly. Lay your baby down on his back, or belly-down across your lap. Insert the thermometer into the rectum until the tip disappears (no more than about 2 centimeters) and hold it in place until the thermometer gives a reading. Gently remove it. This method can sometimes stimulate a bowel movement, so don't be surprised if he suddenly poops!

Additional Tips

  • If you use both rectal and armpit methods, use separate thermometers and label them clearly so they don't get mixed up.
  • Remember to cool your baby off before taking his temperature. You won't get an accurate reading right after he's been swaddled or just had a warm bath.

When to Call the Doctor

According to current recommended guidelines, you should call the doctor immediately if your baby's fever is:

  • Above 100.4 degrees F (if age is less than 3 months)
  • Above 101 degrees F (if age is 3 to 6 months)
  • Above 103 degrees F (if age is 6 months and up)
  • Anytime the fever is accompanied by additional symptoms like coughing, vomiting, diarrhea, an earache or any other worrying condition.