Inevitably, it’ll happen: Your sweet baby will feel warm to the touch, and you’ll wonder if that means your little one has a fever. No problem! You’ll just grab your trusty thermometer and you’ll know in a few seconds. Except…taking a baby’s temperature is not like taking your own temperature. (You wiggle worm can’t hold anything under their tongue!) And now that you think about it, can you even use your thermometer on your baby? And what’s considered a fever in a baby? Before you panic, learn all about how to take your baby’s temperature—and what the results mean.

Thermometers for Baby

Move over, old-school glass thermometer! Today, there are lots of thermometer options for your baby and big kid.

Recommended Baby Thermometers

  • Digital thermometer: According to the American Academy of Pediatrics (AAP), a versatile and quick-reading digital thermometer is the best thermometer to check your child’s temperature. You can use a high-quality digital thermometer to measure the temperature in your child’s mouth (oral), armpit (axillary), or bum (rectal).

  • Ear thermometer: This thermometer, dubbed a tympanic thermometer, measures the temperature inside your kiddo’s ear with an infrared scanner. It’s considered safe to use on babies 6 months and older.

  • Forehead thermometer: Simply swipe this thermometer (also called a temporal artery thermometer) across your bub’s forehead (there’s a major vein there) for an easy and non-invasive temperature read. This device uses infrared scanners to accurately read temperature. 

Thermometers to Avoid

  • Fever strips: Another type of forehead thermometer, these fail to detect 4 out of every 10 fevers, which is why they are not recommended.

  • Mercury thermometer: The classic glass thermometer filled with mercury is not recommended for children, according to the AAP. The thin glass can too easily break and release toxic fumes.

  • Pacifier thermometer: Not only does your tot need to actively suck for up to five minutes, but research shows that the results are inaccurate.

  • Smartphone temperature apps: Quick and easy, yes. But smartphone temperature apps are simply not accurate enough to rely on.

Age-by-Age Guide to Taking Baby’s Temperature

Experts agree the most accurate method for taking your newborn to 3-year-old’s temperature is with a rectal thermometer. Unfortunately, only about 10% of parents opt to take their young child’s temperature this way, according to a 2019 survey in Clinical Pediatrics. Instead, parents prefer taking their tot’s temperature under the arm (41%)...which can be okay, but temps taken in the armpit are considered the least accurate. To know what to use when, follow this guide:

  • Newborns to 3-month-olds: Rectal thermometer is best, but a temporal artery (forehead) thermometer can also be used.

  • 3- to 6-month-olds: Rectal thermometer is preferred, with a temporal artery thermometer being the next best choice. An under-the-armpit check can be acceptable.

  • 6-month to 3-year-olds: Rectal thermometer remains the top choice, but temporal artery and ear methods are good second choices now. The under-arm temperature-check is an okay option.

  • 4-year-old+: A digital oral thermometer is best...if your child can hold the thermometer under their tongue properly. If not, go the rectal, temporal, ear, or armpit route.

Temperature-Taking Cheat Sheet

Most Reliable

  • Rectal thermometer (3 years and under)
  • Oral thermometer (4 years+)

Reliable

  • Forehead thermometer (3 months+)

Less Reliable

  • Ear thermometer (6 months+)

Least Reliable

  • Armpit thermometer
Temperature-taking cheat sheet

      How to Take Your Baby’s Rectal Temperature

      It’s a good bet that so many parents avoid this method of taking their baby’s temperature because they worry that they might inadvertently hurt their little one. But rest assured, if you follow these step-by-step directions, taking your baby’s rectal temperature will be easy…and accurate! (Of course, always follow the instructions that your thermometer came with.) As a reminder: Taking your tot’s temp with a rectal thermometer is the preferred choice until age 3.

      • Step 1: Consider using a disposable thermometer probe cover for easy clean-up.

      • Step 2: Dab a small amount of petroleum jelly on the end of the thermometer and on your baby’s rectum.

      • Step 3: Place your little one on their back with their legs pulled up to their chest. Alternatively, you can lay your baby, belly-down, across your lap or on a firm surface.

      • Step 4: Turn on the device and then push apart your baby’s cheeks with your thumb and forefinger.

      • Step 5: Steady the thermometer between your second and third fingers as you cup your hand against your baby’s bum, and…

        • If your baby is less than 6 months old…gently insert the thermometer about 1/2 inch.

        • If your baby is 6 months old or older…insert the thermometer about 1 inch.

      Many rectal thermometers feature a small ridge near the tip to help you avoid placing the thermometer in too deep.

      • Step 5: Hold the thermometer in place until it beeps.

      • Step 6: Carefully remove the device and check the reading.

      • Step 7: Throw away the disposable probe cover or clean the thermometer thoroughly with soap and cool water—and again with a rubbing alcohol-soaked cotton pad, followed by a rinse.

      How to Take Your Child’s Forehead Temperature

      While fever strips are a definite no-no due to their inaccuracy, using a temporal artery thermometer can be used on children of any age. That said, the AAP urges parents to continue using a rectal thermometer until a child turns 3, as it offers the most accurate reading. To get the proper thermometer reading, follow the instructions that came with your device. While some temporal artery (forehead) thermometers do not need to touch your child’s forehead, others need to be placed on the center of your child’s forehead…and still some others work like this, instead:

      • Step 1: Place the sensor on the center of your child’s forehead. (This thermometer reads the heat coming off the temporal artery, which runs across the forehead.)

      • Step 2: Press and hold the scan button.

      • Step 3: Slowly slide the thermometer across your child’s forehead toward the top of their ear. (Keep the thermometer in contact with their skin.)

      • Step 4: Stop sliding once you reach your kiddo’s

      • Step 5: Look on the display screen to read your child’s temperature.

      • Step 6: Swipe with rubbing alcohol to clean.

      How to Take Your Child’s Ear Temperature

      Tympanic (ear) thermometers can be used on little ones who are at least 6 months old. Young babies’ ear canals are simply too narrow for this method to be used. Again, the preferred and most-accurate method of temperature-taking for kids 3 years old and younger is with a rectal thermometer. While it’s imperative to follow the directions that came with your thermometer, here are the basic how-tos:

      • Step 1: Consider using a disposable thermometer probe cover for easy clean-up.
      • Step 2: Gently pull your child’s ear back…

        • If your baby is 6 to 12 months old…gently pull their ear back and up to open their ear canal.

        • If your child is over 12 months old…gently pull back on the top of the ear to open their ear canal.

      • Step 3: Carefully insert the thermometer until it beeps.

      • Step 4: Gently take out the thermometer.

      • Step 5: Wipe the sensor with rubbing alcohol.

      How to Take Your Child’s Under-the-Arm Temperature

      The “axillary temperature-taking method” is a fancy way of saying under-the-armpit. This popular and convenient strategy is a go-to for many parents, but it’s not super-accurate. Rectal temperature-taking is still recommended for all children 3 years old and younger. And taking your child’s temperature orally is preferred for kids old enough to cooperate, usually at age 4. It’s best to follow your thermometer’s specific directions, but in general, here’s how to take your child’s temperature under the arm—with a digital thermometer (don’t use glass):

      • Step 1: Have your child remove their shirt. (The thermometer must touch skin only, not clothing).

      • Step 2: Ask your child to raise one arm up in the air.

      • Step 3: Place the thermometer under your kiddo’s armpit.

      • Step 4: Have your child fold their arm across their chest to hold the thermometer in place.

      • Step 5: Wait until you hear the thermometer beep to remove and read the temperature. (If the thermometer doesn’t beep, remove it when another ready signal occurs.)

      • Step 6: Clean your thermometer with soap and cool water or with rubbing alcohol, then rinse.

      How to Take Your Child’s Oral Temperature

      Once your kiddo is 4 years old—and can hold the thermometer under their tongue—a digital (not glass!) oral thermometer is your best choice. If the under-the-tongue method proves too tricky, it’s acceptable to keep using a rectal thermometer. You can also opt for a temporal artery (forehead) or ear thermometer…or go the under-the-arm route. Here’s how to take your child’s oral temperature, but always follow the directions that came with your digital thermometer:

      • Step 1: Place the tip of the thermometer under your child’s tongue.

      • Step 2: Ask your kiddo to close their lips around it without biting down or talking.

      • Step 3: Tell your child to relax and breathe normally through their nose.

      • Step 4: Remove the thermometer after you hear the proper number of beeps—or the thermometer otherwise signals that it’s ready. (It usually takes about 30 to 40 seconds.)

      • Step 5: Rinse the thermometer in cool water, then wipe with rubbing alcohol. Rinse again.

      What’s considered a high fever?

      A normal temperature for a baby is about 97 to 100.3 degrees Fahrenheit. (Generally, it hovers around 98.6 degrees, but it can vary from child to child.) You’ll know your baby has a fever when their rectal or forehead temperature spikes to 100.4 or higher (38 degrees Celsius). Any baby under 3 months who has a rectal temperature of 100.4 or higher needs to be seen by a medical professional. Plus, kinds of any age with a fever over 104 degrees should be evaluated.

      Temperature Differences Depending on Thermometer

      Surprise: Not all thermometers offer the same reading. Rectal and forehead temperatures can read slightly higher, whereas ear and armpit temperatures can read slightly lower. That means, if your 2-year-old’s oral temperature is 101 degrees Fahrenheit, their rectal or ear temperature may be about 102 degrees Fahrenheit. Here’s a quick guide to fevers depending on the thermometer you use:

      Your child has a fever if…

      Thermometer              Reading

      Rectal                          100.4 degrees Fahrenheit or above

      Ear                               100.4 degrees Fahrenheit or above

      Forehead                    100.4 degrees Fahrenheit or above

      Oral                             100 degrees Fahrenheit or above

      Armpit                         99 degrees Fahrenheit or above

      Temperature-Taking Tips

      To make taking your child’s temperature even easier—and more accurate—follow these tips:

      • Soothe your child with some white noise, soft talking, and gentle touch.

      • Wait 20 to 30 minutes before taking your child’s rectal or axillary (under arm) temperature if they just had a bath or if they were recently swaddled or cuddled up in blankets. Wait 20 to 30 minutes after your child finishes eating or drinking to take their oral temperature.

      • Wait 15 minutes after coming indoors before using a tympanic (ear) thermometer on your child.

      • Feel your child’s armpits if taking their under-arm temperature. Pits need to be dry before placing the thermometer there.

      • Check for earwax if you’re planning on using a tympanic (ear) thermometer. If there’s a lot in there, find another temperature-taking method. Also, skip the tympanic thermometer if your child has an earache.

      • Label your thermometers indicating which is your digital rectal thermometer and which is your oral use thermometer. Don’t use the same thermometer in both places!

      • Avoid rectal thermometers if your child has leukemia, another cancer, or has a weak immune system due to an organ transplant, HIV, or sickle cell disease.

      • Stay close when taking your child’s temperature. You never want to leave your child unattended while using a thermometer.

       

      Fever Need-to-Knows:

       

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      REFERENCES

      • American Academy of Pediatrics (AAP): How to Take Your Child’s Temperature
      • Mayo Clinic: Thermometer basics: Taking your child’s temperature
      • Sutter Health: Taking Your Child’s Temperature
      • The Centre for Evidence-Based Medicine: Accuracy of strip-like forehead thermometers
      • Cleveland Clinic: Most Accurate Thermometers for Kids
      • Detecting fever in young infants: reliability of perceived, pacifier, and temporal artery temperatures in infants younger than 3 months of age. Pediatric Emergency Care. August 2003
      • The Nemours Foundation, KidsHealth: Taking Your Child's Temperature
      • A Survey About Fever Knowledge, Attitudes, and Practices Among Parents. Clinical Pediatrics. March 2019
      • Seattle Children’s: Fever - How to Take a Temperature (0-12 Months)
      • The Nemours Foundation, KidsHealth: How to Take a Rectal Temperature
      • Stanford Medicine, Children’s Health: Taking a Baby’s Temperature
      • Cleveland Clinic: Thermometers: How to Take your Temperature
      • The Nemours Foundation, KidsHealth: How to Take an Axillary Temperature
      • The Nemours Foundation, KidsHealth: How to Take an Oral Temperature
      • Kaiser Permanente: Fever Temperatures: Accuracy and Comparison

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      Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.