Cohen Medical Associates is a family medical center and research center located in Delray Beach, FL.
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how to take temperature

How to Take Your Temperature Correctly

It’s probably safe to say that at no other time in history have so many people been so occupied with their body’s temperature. It’s important to learn how to get an accurate reading because one of the main signs of COVID-19 infection is a high fever. (Cough and difficulty breathing are the other two symptoms.)

Our family practice doctors in Delray Beach want to review how to take your temperature correctly and when to be concerned with the results.


What is a fever?

A fever is defined as a temperature of 100.4 degrees Fahrenheit (38 degrees Centigrade) or higher. A fever when you’re ill is actually a good sign because it means your body’s immune system is working to fight off an infection.


We’ve all heard that a temperature of 98.6 degrees Fahrenheit is “normal,” but it’s actually an average of humans’ normal temperatures, which can range from 97 to 99.5. Temperatures tend to be lower in the morning and rise throughout the day.


So before you try to learn whether you have a high temperature, you should ideally have established a baseline for what your normal temperature is.


To do this, take your temperature twice a day for a few days to help decide what is normal for you.


What type of thermometer is best?

First, we hope you already have a working thermometer on hand, because they’re as hard to find in stores these days as toilet paper.


Second, if you have one of the old mercury-filled glass thermometers, we recommend you dispose of it as hazardous waste because they can break and expose you to mercury poisoning. Check with your local waste disposal facility for guidance on how to do so safely.


Glass thermometers containing alcohol will be marked “mercury free” and can be used if the person is awake and aware enough not to accidentally bite down on it.


Digital thermometers are the most accurate and easiest to use, and can accommodate all three of the main methods to take a temperature: oral, rectal, and axillary (armpit).


Tympanic thermometers are used to take a temperature inside of the ear, but must be placed correctly to gain an accurate reading. They are not as accurate as digital thermometers used in the mouth or rectum.


The type of thermometer that is placed on the forehead is not as useful as those above, because it records only skin temperature vs. core body temperature.


How to take a temperature accurately

Do not eat or drink anything for at least five minutes before taking your temperature.


Take your temperature twice a day, at the same time each day, or no more than three times a day if you’re ill. Take it before using fever-lowering medication; if you have been exercising, have been exposed to cold or hot weather, or have just had a hot bath or shower, wait at least 20 minutes to obtain an accurate reading.


Start with clean hands and a clean thermometer which has been washed in cold water, then cleaned with rubbing alcohol, then rinsed. If the thermometer has a disposable cover, use after cleaning the device.


Each type of thermometer requires a different method, so be sure to be thoroughly familiar with the literature that came with the device, and never use the same thermometer to take oral and rectal readings.


In general, however, for standard thermometers:


Oral method—Place the thermometer under the tongue, keep your mouth completely closed and breathe through your mouth.


Rectal method—Use rectal thermometers for children up to age three. Lubricate the end with water-soluble or petroleum jelly and insert no more than a half-inch into the rectum.


Axillary method—This method is less accurate, and should only be used for squirming children who won’t hold still long enough to obtain an accurate rectal reading.


When to be concerned

A slight fever is no cause for concern. By “slight” we mean anything below 100.5 degrees Fahrenheit, unless you have other concerning symptoms such as unusual aches, pains, cough, or shortness of breath, or unless an elevated temperature lasts for several days.


Other signs for concern include a fever and:

  • severe headache
  • persistent pain or pressure in the chest
  • bluish lips or face
  • stiff neck
  • confusion
  • swelling of the throat



Young children’s baseline temperatures tend to run a bit higher than adults’, which is why it’s important to establish their normal baseline temperature before they become ill. If they have only a slight fever but are otherwise behaving normally—playing, eating well, etc.—simply monitor them for any unusual signs that they might be ill.


As noted above, different thermometers will give different readings, and a person’s temperature can vary depending on the time of day or what they’ve just been doing.


Whether or not you have a fever, the safest method of all is to assume you are infected with COVID-19 whenever you leave the house. Wear a face covering, stay six feet away from others at all times, and don’t leave your home if you can possibly avoid it.


1 Comment
  • Richard Allen

    How can I take an accurate temperature reading following your instructions? Put the thermometer under my tongue. Keep my mouth closed and breathe through my mouth?

    June 3, 2021 18:06
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