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How is the body temperature measured, and why?

Since Dr. Wilson believes that low body temperatures cause the symptoms and since most patients complain of symptoms they are having during the day, Dr. Wilson recommends that the temperatures be measured during the day.

Body temperatures are normally lower in the morning, higher in the afternoon, and lower again in the evening. So if the temperatures are low during the day when they’re supposed to be at their highest, that’s better evidence that there’s a problem.

Temperature patterns are also important and illuminating. How patients feel can be affected not only by how high or low their temperatures are but also on how steady their temps are. This is especially important during T3 therapy. One temperature reading a day is not enough to see how widely the temperature is fluctuating, but more than three a day can be too time consuming.

For these reasons Dr. Wilson recommends measuring the temperatures

  • By mouth with a thermometer
  • Every 3 hours
  • 3 times a day, starting 3 hours after waking
  • For several days (not the 3 days prior to the period in women since its higher then) for diagnosis.
  • Every day during treatment.

Here is a convenient temperature log you can print out and use to record your temperatures.

For each day, add the 3 temperatures together and divide by 3 to get the average.

If your temperature consistently averages below 98.6 then you may be suffering from Wilson’s Temperature Syndrome.

Note: Some people believe that moving the thermometer around in the mouth very much can increase blood flow to the area and affect the temperature reading. It seems prudent to be mindful not to move the thermometer unnecessarily much.

Go to How are Body Temperatures Measured? for more information.

About the Author:

Denis Wilson, MD developed the concept of Wilson 's Temperature Syndrome in 1988 after observing people with symptoms of low thyroid and low body temperature, yet who had normal blood tests. He found that by normalizing their temperatures with T3 (without T4) their symptoms often remained improved even after the treatment was discontinued.


  1. robin June 24, 2014 at 9:13 am - Reply

    If temperatures are normally lower in morning and evening, doesn’t that mean the average will most always be under 98.6, unless the afternoon temperature is well above 98.6? I have been doing the protocol for a few weeks now, and got up to 60 mcg, and started having side effects. I am cycling down, and may try another round, but I noticed my 3 daily temperatures followed your example, lower in morning and night, higher in afternoon, but not averaging 98.6. I just thought that mathematically, when 2 of 3 numbers are low, the average most likely will be lower also.

    • Dr. Denis Wilson July 2, 2014 at 6:25 am - Reply

      Yes, I agree with your math. If a person wakes up at 7am we recommend temps at 10, 1, 4 pm. That excludes early morning and evening temperatures. We are looking for the average of those 3 numbers (10, 1, 4). That is a good guide. 1pm would not always be the highest reading but it might be.

  2. Patricia Moreau April 19, 2016 at 8:21 am - Reply

    I Have always had low body temperature. I am usually in the 96s sometimes even 95’s. I never get fevers but for me , 98.6-7 is a fever to me. I have been saying this to my Doc but he thinks it’s just me. My Doc is a smart man so I don’t always question him. I have alot of autoimmune problems, IBS, Orthostatic hypotension, chronic fatigue, urinary inconvenience, probably things undiagnosed since I have multiple lesions in my brain,lungs who knows if anywhere else. My question: do you think my problems are from Always having low temperatures? Or do you think my problems cause low temperatures? I am curious, I hope for new findings to feel better all the time. FYI, my thyroid has been checked many times, always normal.

    • Dr. Denis Wilson April 24, 2016 at 7:03 pm - Reply

      That’s a great question. Low temps can explain health problems and health problems can bring on low temps. This can contribute to a vicious cycle and can help explain why some people stay with low temps and symptoms long after the precipitating stress has passed.

  3. Kayla Dean June 23, 2016 at 6:17 am - Reply

    I was told to take my temperature under my arm. I’ve been doing so for a few days now, but I am curious, should I add a degree for temps taken this way?

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