How to Take a Child's Temperature

Illustration of child sick in bed with different types of thermometers

Verywell / Jiaqi Zhou

Caring for a child who might have a fever can be stressful. But on top of that, many parents feel unsure about how to go about taking their child’s temperature. You may be wondering what type of thermometer to use, the best way to use it, how often you should take the temperature, how you clean the thermometer, and which thermometer gives the most accurate reading. And the list goes on.

These are common and understandable questions—and we’ve got answers. Here is a simple breakdown of which thermometer to use based on your child’s age and needs, how to use them, what the readings mean, and what to do if you discover your child has a fever.

Types of Thermometers

The method you use to take your child’s temperature will vary based on your child's age. Babies can’t easily or safely use an oral thermometer, for example. And as your child gets older, taking their rectal temperature becomes nearly impossible, and unnecessary.

Always Use A Digital Thermometer

It’s important to note that whatever type of thermometer you use, it is no longer advised that you use a mercury-containing thermometer, under any circumstances. Instead, the Academy of American Pediatrics (AAP) recommends that all parents only use digital thermometers.

As the AAP explains: “Do NOT use a mercury thermometer. These thin glass devices filled with the silvery metal can break and release toxic levels of mercury fumes.”

The AAP advises that if you still have any mercury filled thermometers at home, you should dispose of them promptly, and replace them with digital thermometers.

Thankfully, these days, digital thermometers are found abundantly online and in most drug stores or baby stores—and their cost is generally manageable. Besides being the safer choice, digital thermometers can give you accurate readings of your child’s temperature within about 10 seconds. This is a great advantage when you are dealing with a cranky baby or child!

A multi-use digital thermometer can be used for rectal, armpit, or oral readings, though each thermometer should be reserved for only one of these uses. Digital forehand scanners as well as digital ear thermometers can also easily be purchased in stores or online.

There are three basic types of digital thermometers:

  • Multi-use thermometers
  • Forehead thermometers (temporal artery)
  • Ear thermometers (tympanic)

Multi-Use Thermometers

These types of thermometers can be used rectally, orally, or in the armpit. A small sensor at the tip of the thermometer reads your child’s temperature.

Again, it’s important not to use the same thermometer for both rectal and oral readings. It’s best to purchase more than one multi-use thermometer, and label each according to use.

Forehead Thermometers (Temporal Artery)

These thermometers measure heat waves coming off your child’s skin. Most of these are “no contact” thermometers, thereby potentially reducing the spread of germs. Temperature is taken from the front and side of your child’s forehead. Just follow the specific directions for the forehead thermometer you purchased.

Ear Thermometers (Tympanic)

This type of thermometer reads heat waves in your child’s eardrum. It is not to be used on babies younger than six months, and must be placed properly in your child’s ear to get an accurate reading.

Which Thermometer to Use, Based on Age

Let’s take a look at which temperature taking method is best, according to your child’s age. These are all age approximations, and there might be a different method that works best for your child. If you have any questions about your particular child, consult your doctor.

Babies

In general, rectal temperature readings are the most accurate for babies, followed by forehead (temporal artery) temperature readings.

Sometimes a doctor will use an armpit reading to screen your baby for a fever, and then take a rectal temperature if a fever is indicated. You may also do this at home. However, armpit readings are the least accurate temperature taking method, which is why they are only used for screening purposes.

Once your baby is six months old, you can consider using an ear thermometer to take their temperature. However, ear thermometer readings are not as accurate as rectal or forehead temperature readings, especially if not done correctly.

Toddlers and Preschoolers

Rectal, forehead, and ear temperature readings are recommended until your child is four years old, though ear temperature readings may be less accurate than rectal and forehead readings.

Older Children

Once your child is four years old, their temperature can be taken orally. However, your child’s ability to use this method well and to feel comfortable with it might not happen the day they turn four.

All children are different, and if your child resists it, taking their temperature orally is something you can build up to. While you wait, taking a forehead temperature or an ear temperature might be more possible.

How to Use Each Type of Thermometer

Knowing which type of thermometer to use is one thing. Actually taking a squirming child’s temperature is something else.

When you are first starting out taking your child’s temperature, it can be really helpful to have another grown-up nearby to help. Either way, understanding how to do it, and having any supplies at hand before you start, can be immensely helpful.

To get an accurate reading, it’s always important to follow the instructions that come with your thermometers.

Rectal Thermometer

Rectal thermometers are the best option for babies under three months, and can be used for babies and toddlers. Because inserting a thermometer into your child’s rectal area must be done carefully and gently, it’s important to familiarize yourself with how to do it and to gather up any supplies beforehand.

  1. Start by lubricating the thermometer. Most doctors recommend petroleum jelly for this. You can also put some lubricant on your baby’s buttocks area before you start.
  2. Lie your child on a flat surface. You can either place them on their belly or their back. If you place your baby on their back, you will want to pull their legs gently up to their chest.
  3. Gently place the thermometer into your child’s anus, about ½ an inch to 1 inch. Do this gently and never force it.
  4. Keep the thermometer in place until it beeps. At this point, the reading has been taken.
  5. Keep supplies on hand for clean-up. It’s common for babies to pass stool after having their temperature taken, so watch out for that.
  6. Wash thermometer. You can use soapy water or disinfected with alcohol swabs after each use.

Oral Thermometer

You should wait until your child is four to take their temperature orally. Even then, some children will not be ready to hold still long enough for this method to be effective.

  1. Turn the thermometer on first. Then place it under your child’s tongue.
  2. Ensure proper placement. The thermometer needs to be placed toward the back of your child’s mouth, and steadily held in place during the reading. Don’t have your child bite down on the thermometer; they can use their hand and lips to keep it in place. Your child’s lips must be sealed around the thermometer
  3. TIme it right. You should wait about 30 minutes after your child has had a cold or hot food before using this method.

Ear Thermometer

  • Read the package insert carefully before using this method.
  • You must position the thermometer correctly in your child’s ear; usually this means aiming the tip between the opposite eye and ear.
  • You should wait at least 15 minutes before taking your child’s temperature with this method if they have recently been outside.

Forehead Thermometer

  • Read the package insert carefully before trying this method.
  • The instructions will tell you where on your child’s forehead to aim the thermometer, how far from your child’s forehead to hold it, and how long it will take to get an accurate reading.

Which Type of Thermometer Is Most Accurate?

Rectal temperature readings are considered most accurate. Forehead readings are considered reliably accurate as well. Ear and oral readings can be accurate, but only if they are done properly, and there is room for errors, especially among younger children.

Armpit temperature readings don’t usually give precise readings, but they can be used to give a ballpark estimate of your child’s temperature. If the armpit temperature indicates fever, another more accurate method can be used. Forehead temperature strips aren’t considered accurate either.

How to Clean a Thermometer

Thermometers should be cleaned before and after use. Always follow the package insert’s instructions for cleaning your child’s thermometers.

In general, multi-use digital thermometers can be cleaned with soap and water or alcohol wipes. Forehead thermometers and ear thermometers are usually best cleaned with alcohol wipes or cotton balls dipped in alcohol.

How Often to Take Your Child’s Temperature

If your child has a fever, but is otherwise happy and well, you don’t have to take their temperature more than a few times a day. However, if your child is very sick, under three months old, or seems to be spiking a higher fever, consider taking their temperature every few hours, as needed.

It’s common for temperatures to fluctuate throughout the day, and to rise in the evening and at night.

What Temperature Is Considered a Fever?

What is considered a baseline temperature for each child varies slightly; as such, what is considered an elevated temperature can vary from child to child.  

According to the Academy of American Pediatrics (AAP):

  • Your child’s temperature is usually considered a fever if it rises above 100.4 degrees Fahrenheit, or 38 degrees Celsius.
  • Any type of fever in a child under three months is considered serious and requires an immediate call to the doctor. In babies under two months, 100.4 degrees Fahrenheit is considered a fever.
  • Fevers above 104°F (40°C) at any age is considered a medical emergency.

What to Do If Your Child Has a Fever

Sometimes children can have low fevers and actually be seriously ill. At other times, children can have high fevers and be happy and comfortable. So temperature alone isn’t the most important thing when it comes to children and illnesses.

As the Academy of American Pediatrics (AAP) describes it, a child’s fever should be considered serious and warrant immediate medical attention if:

  • The child is two months old and has a rectal reading over 100.4 degrees Fahrenheit; fevers in young babies should always be taken seriously.
  • Your child seems very lethargic, can’t be roused from sleep, or is especially cranky or fussy.
  • Your child has symptoms such as a stiff neck, vomiting/diarrhea, a new or unusual rash, or severe headache, sore throat, or ear pain.
  • Your child has had a seizure.
  • Your child has a history of immune diseases, cancer, or is currently taking steroids.

Besides illness, remaining in a very hot place, such as a hot car, can cause elevated body temperatures. If your child becomes overheated suddenly and shows signs of heat stroke (hot, lethargic, rapid heartbeat, labored breathing, confusion, loss of consciousness), cool and hydrate your child immediately, and seek medical attention.

A Word From Verywell

When it’s the middle of the night and your little one is fussing and seems warm to the touch, the last thing you want to be doing is trying to figure out which thermometer to use to take their temperature and how to go about doing it.

That’s why it’s good to familiarize yourself with the different types of thermometers out there and consider trying them out before using them for the first time.

But the good thing is that knowing which thermometer to use and how to use it is actually simpler than you might think—and these days, there are so many options in terms of type of thermometer and which method might work best for your child.

Remember, too, that you don’t have to go it alone. If you have any questions or concerns about how to take your baby’s temperature, you should ask your pediatrician. They have a lot of experience in this, and will be happy to help you.

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  1. Healthy Children. How to Take Your Child’s Temperature. Updated October 12, 2020.

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