Fort Worth, Texas,
12:35 PM

7 Types of Thermometers and to what Degree You Should Trust Them

Generally, I’m not too concerned about the exact number of your child’s temperature. “Felt warm” is usually more than enough for me to know my kid has a fever.

But, like many things in medicine, that has changed in the world of COVID-19.

Many of the protocols for screening and testing have been developed based upon knowing if you or your child has fever.

So, now more than ever, knowing which type of thermometer and the best way to take your temperature is crucial.

Here is a look at 7 different types of thermometers (and a bonus one that many of you swear by) and how to decide if they are right for your family:

1. Forehead strips

Ahh…the allure of not having to wake your baby up to know their temperature. Sounds nice, right? And it might even offer you some peace of mind. But is that peace of mind false? Probably. There aren’t many studies on the use of strip thermometers but most recognize the accuracy of detecting fever at around 35 to 50 percent. What does that mean? If you don’t want to touch your child and wake them up to see if they have a fever, just flip a coin…Heads=fever, Tails=no fever.

2. Wearable thermometers

Trying to one up the forehead strips is the wearable thermometer. In theory, it will notify you via an app if your child’s temperature reaches a fever. Like the forehead strips, the accuracy of these is suspect. On top of that, if you’ve read anything I’ve written about fever before (like this post about fever myths), you might know that I don’t think it’s important to know your child’s temperature every second of the night.

3. Pacifier thermometers

Just plain “Nope.” They don’t work. Save your money.

4. Ear thermometers (tympanic)

Now we’re getting into the more common and reliable ways of checking your child’s temperature. While not my favorite, some parents like the relative ease of the tympanic thermometer. This thermometer is placed in the ear. A few important points: 1) It can’t be used in children under 6 months. 2) Placement in the canal matters. Read the directions and follow them. 3) Excess earwax can cause an incorrect reading.

5. Forehead thermometers (temporal)

This is the preferred method for most kids 3 months and over, particularly for screening when you can’t or prefer not to do a rectal temperature. That’s why you’ll find most doctor’s offices using them at check-in. Once again, the placement and the way you move it matters so follow the directions included. If you are getting a reading that doesn’t make sense, check it a few more times until you are getting consistent readings. Another nice thing about these thermometers is that they can be used for screening even before 3 months of age…before you go to take a rectal temperature.

6. Digital thermometers

A nice digital thermometer is good to have because it can be used throughout age ranges, provides accurate readings, and it's cheap.

At any age, you can use a digital thermometer under the arm and add 1 degree to get a general sense of what the true temperature might be (just don’t count on that as 100-percent reliable.)

Before age 3, the most accurate temperature will be a rectal temperature, in the bottom (see below for how to take a rectal temperature). Anything over 100.4 taken rectally is a fever. After age 4 or 5, you can start to take the temperature in the mouth (see below for how to take an oral temperature). I general consider 101.4 or above to be a fever when taken orally.

7. Non-contact Infrared Thermometers

With the recent events related to COVID-19, I've gotten a lot of questions about these thermometers. They are an option for you because they are accurate, can be used for screening at your home or office and they don't require touch.

Bonus: Mom’s hand or lips

“He feels about like the oven which is set at 350 degree.” Actual phone call. Actual quote.

Ok, this is not an actual thermometer, but I thought it deserved a mention. While touching the child might give you an idea that you should check a temp, mom’s hand is not a reliable way to determine the child’s temperature. Now grandma’s hand…I find it best not to argue with grandmas. “It felt like 102…yes ma’am.” But seriously, use an thermometer that works.

Hopefully this article will provide you some guidance for the next time you need to replace your thermometer. You have a few solid options and a few terrible ones. Some are basic but work just fine. Some have fancier features that might be useful. Others have stuff which prove that the solution to fever is not always more (cow)bells and whistles.

How to take a rectal temperature

  • Clean the thermometer with soap and water.
  • Place a small amount of petroleum jelly on the end.
  • Place your baby across your lap face down or on their back on a firm surface.
  • Gently place the thermometer about ½ inch into the anus.
  • Place your entire hand around the child’s bottom, holding the thermometer in place between your fingers.
  • Hold in place for about 1 minute or until you hear the beep.

How to take an oral temperature

  • Wait 10-15 minutes after the child has had a drink.
  • Clean the thermometer with soap and water.
  • Turn the thermometer on and place under the tongue toward the back of the mouth.
  • Wait for 1 minute or until you hear the beep.

Get to know Justin Smith, M.D.

Justin Smith, M.D., is a pediatrician in Trophy Club  and the Medical Advisor for Digital Health for Cook Children's in Fort Worth, Texas. He has an active community on both Facebook and Twitter as @TheDocSmitty and writes weekly for Cook Children's He believes that strategic use of social media and technology by pediatricians to connect with families can deepen their relationship and provide a new level of convenience for both of their busy lifestyles. Dr. Smith’s innovative pediatric clinic, a pediatric clinic “designed by you,” open now. Click to learn more. To make an appointment, call 817-347-8100.

Comments 1 - 4 (4)
Thank you for your message. It will be posted after approval.
Komal Kumari
Thank you
Good explanation
Thanks so much for this! Was worried I needed to return the temporal thermometer I got after a labor & delivery nurse told me docs don't like those. Glad I can use it for a screening and then see if need to take a rectal temp. Thanks for the clarification!
Petra kpeglar
Good definitions they help