Types of Thermometers

You have the option of digital or manual (mercury) thermometers for taking a temperature in three ways:

Oral Rectal Axillary (armpit)

Two other types of digital-only thermometers are available:

Tympanic (ear)Temporal (forehead)

The American Academy of Pediatricians recommends digital thermometers for taking a child’s temperature because they’re fast and accurate. The specific type of digital thermometer they suggest varies by age.

Oral Thermometer Use

Oral thermometers are not the best option for young children, who may not be able to keep their mouths closed long enough to get a good reading.

To use an oral thermometer:

Wash your hands before handling the thermometer. Place it under the tongue. Make sure the mouth stays closed the entire time. Wait approximately five minutes (manual thermometer) or for the beep (digital thermometer).

Axillary Thermometer Use

While this is the least accurate way to get a child’s temperature, it’s often used in schools and daycare to avoid spreading germs.

To use an axillary thermometer:

Place the thermometer under the arm with the tip in the deepest crease of the armpit. Wait approximately five minutes (manual thermometer) or for the beep (digital thermometer).

Rectal Thermometer Use

Rectal thermometers are specifically designed with short tips that allow them to get a proper reading without going too far into the body. This method should be used for infants or those whose temperature cannot be taken any other way.

To use a rectal thermometer:

Use lubrication, such as petroleum jelly, to ease insertion. Place the thermometer’s tip in the rectum. Wait approximately five minutes (manual thermometer) or for the beep (digital thermometer).

Tympanic Thermometer Use

These in-the-ear thermometers are very popular, especially among parents of small children, since they’re faster than regular digital thermometers and are easy to use. However, tympanic thermometers can be difficult to use on babies and are often inaccurate because their ear canals are so small. 

To use a tympanic thermometer:

Pull the top of earlobe up and backPlace the tip of the thermometer (covered with probe cover) in the ear-canal opening. (Be sure you are pointing the probe into the ear canal opening and not at the wall of the ear. )Press the button until it beeps.

Make sure excess earwax isn’t built up before using this method, as it can cause less accurate results.

Temporal Thermometer Use

The newest and most expensive thermometer on the market, temporal thermometers read heat coming from the temporal artery, which is right under the skin of your forehead. They are the fastest and probably the easiest thermometers to use. However, they may read too low at times.

Different models may have different instructions for use. Generally, to use a temporal thermometer:

Press the button down. Sweep the probe across the forehead and release the button when done.

Note: Some models require a swipe across the forehead and on the neck below the ear.

This is fairly new technology, but research suggests that it’s at least as accurate as tympanic devices.

Mercury Thermometers

Mercury thermometers are no longer sold in the United States. They pose a danger if they break and release the mercury, which is toxic.

If you have an old mercury thermometer that you decide to use, shake it to get the mercury down to below 96 degrees F. Then hold it in place for about five minutes to get an accurate reading.

Temperature Ranges

The “normal” body temperature is usually stated as 98.6 degrees F. However, there’s actually a range of body temperatures that’s influenced by all kinds of factors, including age, height, weight, sex, ethnicity, and even time of day and activity level.

Interestingly, what’s average appears to have dropped over time. A 2017 study found that the average body temperature is closer to 97.88 degrees F. This is relatively new information, though, and it hasn’t yet impacted what the medical community considers normal and abnormal.

Certain temperatures or symptoms do warrant medical attention, though.

When it comes to your child, you should call the doctor when:

A baby 3 months old or younger has a temperature of 100. 4 degrees FA child of any age has repeated fevers over 104 degrees FA child under 2 has a fever of 100. 4 that lasts for more than 24 hoursA child 2 or older has a fever of 100. 4 lasting more than 72 hoursYour baby cries or fusses and can’t be soothed

For an adult, you should call the doctor if you have a fever:

Over 103 degrees F that doesn’t drop within two hours of taking a fever reducerThat lasts longer than two daysThat’s in the high range and accompanied by a rashThat’s accompanied by a stiff neck and confusion or irritability, sensitivity to light (photophobia), dehydration, or seizure

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