Fort Worth, Texas,
09:12 PM

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

The Doc Smitty also has tips on how take temperatures

It’s 3 a.m. and your child wakes up feeling like an oven. Quick! Where’s your thermometer?

The preceding message was a drill.

A drill that I should practice more often because when the heat is on, I flame out every time.

Let’s assume you are organized enough to know where your thermometer is...What’s the best way to take a child’s temperature? You know there are 1,000 options. There are 1,000 ways to do it. But what’s the best way?

Here is a look at 7 different types of “thermometers” and to what degree you should trust them.

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 give 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 35-50 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 guess 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 useful 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…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. Mom’s hand or lips

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

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…I find it best not to argue with grandmas. “It felt like 102…yes ma’am.”

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 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 - 2 (2)
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Petra kpeglar
Good definitions they help
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!