What kind of thermometer should I use?
If you think your baby has a fever, it's important to know exactly what his temperature is, so you'll need a good digital thermometer. We'll help you choose one. (Get more details in our thermometer buying guide.)
Regular multi-use digital thermometers are sold in drugstores for less than $10. They're easy to use, easy to read, and fast – typically giving a reading in 10 seconds to two minutes. Most can be used rectally, orally, or under the arm, although taking your child's temperature orally won't be an option until he's at least 4 years old. If you have a multi-use thermometer, designate it for just one area to avoid spreading bacteria.
Taking your baby's temperature rectally will give you the most accurate result, and the best tools for this are rectal thermometers, which are designed specifically for this purpose. Look for one with a flexible tip and a wide handle that won't let you insert the thermometer more than an inch. Inserting it farther can perforate your child's rectum.
More expensive options include temporal artery thermometers, which use an infrared scanner to measure a baby's temperature with a simple swipe across the forehead, and tympanic (ear) thermometers, which can be trickier to use.
Doctors say other temperature-taking tools, such as pacifier thermometers and temperature-sensitive strips that you place on a child's forehead, are too inaccurate to be useful.
Whichever method you choose, don't take your child's temperature right after a bath, when his body temperature is likely to be temporarily elevated. Wait at least 20 minutes after bath time for an accurate reading. The same is true if your baby's been swaddled.
Note: Old-fashioned glass thermometers can shatter and leak toxic mercury. If you still have one around the house, learn how to dispose of it properly. (Check online to find the nearest household hazardous waste site.)
How to use a rectal thermometer
Some babies don't mind having their temperature taken rectally, while others seem to hate it. If your baby protests, you might want to take her underarm (axillary) temperature first. If that reading is over 99 degrees Fahrenheit, take her rectal temperature for a more precise and accurate result.
- To prepare the thermometer, clean the end with rubbing alcohol or a little soap and warm water. Rinse with cool water. Then coat the end with a little petroleum jelly for easier insertion.
- Place your baby on her back, on the bed or on a changing table, with her legs bent to her chest. Your baby is likely to be comfortable in this position, since she's used to lying that way for diaper changes. And you'll be able to distract her if she can see your face. Alternatively, though, you can hold your baby across your lap, tummy down and bottom up, letting her legs dangle over the side of your thigh.
- Press the thermometer button to turn it on. Gently insert the bulb about three-quarters of an inch to an inch (2 to 2.5 centimeters) into her rectum, or until the tip of the thermometer disappears.
- Keep a firm grip on her buttocks by cupping them with the palm and fingers of the hand that's holding the thermometer. Don't let go of the thermometer, because it may not stay in place if your baby starts wriggling.
- When the thermometer beeps, remove it and read your baby's temperature. Inserting anything into your baby's rectum can stimulate her bowels, so don't be surprised if she poops when you take the thermometer out. Clean the thermometer with soapy water or rubbing alcohol, then rinse and dry before storing.
How to use a temporal artery (forehead) thermometer
Temporal artery thermometers are very easy to use – once you know how to use them.
Be sure to read the directions carefully. If you don't have the directions at your fingertips, you should be able to find them online on the manufacturer's website. If you have difficulty, ask your doctor for guidance.
The basic technique involves positioning the thermometer flat on your child's forehead midway between the eyebrow and the hairline. Press the button and – keeping the thermometer in contact with your child's skin – swipe the thermometer in a straight line across the forehead (not down the side of the face).
Without releasing the button, lift the thermometer off the forehead. Then release the button and read the temperature.
The way temporal artery thermometers determine temperature is quite sophisticated, but essentially the reading is based on an artery that is close to the surface of the skin in the forehead.
How to take an armpit temperature
Some doctors recommend taking a baby's temperature in the armpit. This is called the axillary temperature. It's easy, convenient, and safe, and all you need is a regular digital thermometer.
The downside is that an armpit reading is far less accurate than other methods. An armpit reading, which is external, can be as much as 2 degrees lower than an internal rectal reading. The American Academy of Pediatrics (AAP) says it's better not to use this method for babies under 3 months of age, when an accurate reading is most important.
For an armpit reading, undress your baby from the waist up and cradle him or sit him on your lap or next to you. Try to keep him relaxed and occupied by feeding him or showing him a book or a toy.
Make sure your baby's underarm area is dry, then slip the bulb of the thermometer into his armpit. The bulb needs to be in full contact with his skin, so hold your baby's arm firmly against his side or bent and folded across his chest. When the thermometer beeps, take it out and read the display.