Best Baby Thermometers

While you might suspect your infant has a fever simply by feeling her forehead, you'll still want to use a reliable baby thermometer to get an exact reading.

Although most fevers in babies are triggered by viral infections and run their course on their own, a fever can also potentially be more serious (especially in the COVID-19 era), so a baby thermometer that gives you an accurate reading is essential.

In general, a reading of 100.4 degrees Fahrenheit or higher on a rectal thermometer (which is recommended for newborns under 3 months) is considered a fever in babies. While you might want to rush and call your pediatrician right away, there are a few factors to consider first, such as your baby's age and how long the fever has lasted.

"Fevers can seem scary, but they are a natural immune response to infection and most can be safely managed at home," says Steph Lee, M.D., a pediatrician specializing in preventive medicine and spokesperson for the American Academy of Pediatrics (AAP).

Ahead, we've answered a few important questions regarding infant fevers and what to know about the different types of thermometers and then rounded up some of the best baby thermometers to consider.

When to call your doctor if your baby has a fever

If you're wondering what's considered too high for a baby's fever, you should know that it varies depending on baby's age, how long the fever has lasted and whether there are other symptoms.

Seek emergency medical attention if:

• Your baby is under 3 months old with a fever of 100.4 degrees F or higher.

Call your doctor right away if:

• Your baby is between 3 and 6 months old with a fever of 102 degrees F or higher.
• Your baby is between 6 and 24 months old with a fever of 102 degrees F or higher for more than 24 hours.
• Your baby has a fever that lasts more than three days.

There are some additional symptoms that warrant a call to your doctor, such as those associated with dehydration (fewer than six wet diapers in 24 hours, not taking in or keeping down liquids, a dry mouth or crying without tears), severe symptoms like stiff neck and vomiting, or if your child isn't acting like herself (she's lethargic or not eating, for example).

Otherwise, if your child doesn't meet the above criteria, you can take care of baby's fever at home by keeping her cool with lightweight clothes, sponging her with lukewarm water and making sure she's hydrated. Medicine isn't always necessary in bringing down a fever, but if these home remedies aren't helping, you may want to try a fever reducer. Only babies over 3 months old can take infant's acetaminophen (Tylenol) while babies over 6 months old can have infant's ibuprofen (Motrin or Advil). However, the AAP recommends always contacting your doctor before giving children under 2 years of age medicine for fevers.

If you're unsure or worried, it's always smart to err on the side of caution and call your doctor with any concerns you have about your baby's health. "When in doubt, a [parent's] intuition is always a good reason to seek care," says Dr. Lee.

Types of baby thermometers

There are several different types of baby thermometers out there, and a few factors you'll want to consider when deciding which one to buy.

• Rectal thermometers: A rectal thermometer is recommended in order to get the most accurate temperature. "In newborns and kids up to 3 years of age, the AAP recommends rectal thermometers, because research shows they are the most accurate and measure the core body temperature the best," says Dr. Lee. While you can switch to another thermometer as baby gets older, you should use this type at least until baby is at least 3 months old. This is not only because of their accuracy, but also because other types might be difficult or uncomfortable to use with newborns.
• Forehead thermometers. A forehead thermometer is simple to operate: You either run it across your baby's forehead or hold it a short distance above the forehead to get a reading. While they're not as accurate as rectal thermometers, they can give you an idea of your child's temperature and, in the case of ones that don't need to touch their skin, can allow you to take a temperature while your baby is sleeping, says Daniel Ganjian, M.D., a pediatrician at Providence Saint John's Health Center in Santa Monica, Calif. This is helpful if you have a baby who struggles to keep still.
• Ear thermometers: This type of thermometer, which is conveniently placed inside your baby's ear, is easier to use than a rectal thermometer, but not as accurate. That said, they provide hassle-free readings and typically deliver results in just a few seconds. Keep in mind that the AAP doesn't recommend using ear thermometers for babies under 6 months, since their ear canals are too small to allow you to get a proper reading.
• Oral thermometers: Once kids are able to cooperate — usually when they are around 3 or 4 years old — parents can use oral thermometers, which are placed under your child's tongue. "The only downside is that the child has to keep the thermometer under their tongue for around a minute, so if this isn't possible, parents may not get an accurate reading," Dr. Lee says. "However, if used correctly, oral thermometers are accurate and approximate core body temperature well."
• Axillary thermometers: Also called underarm thermometers, these types of thermometers are placed against the skin in the armpit and generally work best in toddlers who can cooperate and hold the thermometer in place without moving until the thermometer beeps. However, per the AAP, it is the least accurate method of temperature-taking.

What all these types of thermometers have in common is that they're digital, which is what you should always use, per the AAP. And, be sure to never use a mercury thermometer, as mercury is an environmental toxin and can be especially dangerous if the thermometer were to break. They're harder to find these days in the U.S., although grandparents might have some legacy mercury thermometers in the back of their medicine cabinets, so just be aware.

One other aspect to keep in mind is that sometimes thermometers are multi-functional — meaning they could work as rectal, oral or armpit readers — but you should never use a thermometer that has been used rectally for anything else. The AAP suggests having multiple thermometers and labeling them "rectal" and "oral" so you can easily tell the difference.

What's the most accurate baby thermometer for infants?

As stated previously, rectal thermometers are the most accurate for infants, according to the AAP.

Many parents find underarm thermometers or ear and forehead thermometers easier to use on their children, but for the most accurate results, you should ideally follow up with a rectal reading, especially when taking a young baby's temperature.

What to look for in a baby thermometer

Here are a few features you may want to look for when shopping for a baby thermometer:

• Readability: A backlit display can make the thermometer easy to read when checking baby's temperature in a dark nursery. A baby thermometer that reads you the temperature may also be helpful in the middle of the night,  if the display is difficult to read, or the caretaker has impaired vision.
• Fast Results: Most thermometers will deliver results in seconds, but the difference of just a few seconds can mean everything when you're trying to take the temperature of a wriggling, fussy baby. Some thermometers deliver results instantly, while others can take up to 60 seconds, so you'll want to make sure you know the speed of each model if fast results are important to you.
• Comfort: Comfort is most important when it comes to rectal thermometers so you don't upset baby any more than you have to, especially while she's feeling unwell. Having a feature like a flexible tip can provide more comfort for baby when you insert a rectal thermometer, while some are designed specifically for babies and feature a short probe and stopper to ensure you don't insert it too far.
• Accuracy: A rectal thermometer will give you the most accurate temperature readings for babies, so you'll want to make sure you have one on hand. However, as your baby gets older, you can try different types of thermometers.
• Ease of Use: There are a few features that can make baby thermometers easier to use or more functional than the basic action of taking temperature. For instance, if a rectal thermometer has a wide base, you'll have an easier time gripping the base as you're inserting it. Some thermometers have high-tech features and can connect to an app to remember baby's temperatures so you can track any trends. You might also be interested in multi-use thermometers that can be used on both the ear and forehead.

How we chose the best baby thermometers

Sorting through the many different baby thermometers on the market can be overwhelming. To choose the best baby thermometers, we interviewed three pediatricians: Dr. Lee, Dr. Ganjian and Ashanti Woods, M.D., a pediatrician at Baltimore's Mercy Medical Center, for input on the essential factors to have in a thermometer, such as fast results, accuracy and comfort. We also considered elements like ease of use, readability, comfort and accuracy to help you know what to look out for when shopping. To find a consensus on which baby thermometer parents like the most, we looked to recommendations from the millions of parents in the What to Expect Community to help you find the right option for your family.