Posted on: August 10, 2015 at 4:16 pm
Last updated: May 4, 2018 at 12:14 pm

The Barnes Thyroid Test was developed by Broda O. Barnes, M.D., Ph.D, a physician in Colorado. He found over 50 years ago that body basal temperature was a good indicator of thyroid activity, in particular, the body temperature when arising from sleep. It is Dr. Barnes opinion that this test is superior to standard blood tests to evaluate thyroid function. Blood tests only measure pituitary (TSH) and T3 hormone blood levels while temperature readings measure how much energy is actually being generated in the cells.

If the thyroid is running low, the body’s temperature will drop below normal while the body is resting or asleep. This test is performed by measuring the underarm temperature when you awaken in the morning. To develop an accurate reading the test is done for five consecutive days and the mean average is calculated. You will need a basal thermometer for this test.

Do not test when you have an infection or any other condition that would raise your body temperature.

Do not use an electric blanket for 24 hours prior to taking your temperature.



  1. The night before your test, shake down a thermometer below 95 degrees and leave it on your nightstand.
  2. When you awaken, without raising your head from your pillow, place the thermometer under your arm, with the bulb of the thermometer under the armpit.
  3. Leave it there for ten minutes, while resting on your back. Moving around too much will activate the thyroid gland and you get a false reading.
  4. After ten minutes remove the thermometer and write down your temperature.

This temperature reading is your basal temperature. A “normal” range should be between 97.8 and 98.2.

To figure your average, add the temperature reading for all five consecutive days and then divide by 5.

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If the thyroid is overactive, your temperature will show 1-2 degrees above normal.

If the thyroid is underactive, your temperature will show 1-2 degrees below normal.


If your results are concerning, blood tests for evaluating thyroid function may be indicated.

It is important to be aware that even blood tests can come back showing thyroid function within a normal range even if the thyroid is malfunctioning. The reason for this is because a standard test will show only how much thyroid hormone is circulating in the blood and doesn’t show how the hormones are functioning on a cellular level. Also, the loss of up to 70% of thyroid function may occur before a blood test will show an abnormal result.

This was certainly the case in my own blood tests which showed thyroid function well within the normal range. Yet I had little to no energy, and was simply exhausted most of the time. After the additional of iodine supplements there was a significant difference in my energy level. I had more stamina throughout the entire day, as opposed to being exhausted by 4 p.m. and struggling to get through the rest of the evening.

Click here for article on Iodine Patch Test for additional information and home test options.

A reader has noted: “The article states to shake the thermometer down to 95 before bed. Then in AM place the bulb under your arm for 10 minutes. Digitals take quick readings after temps have been reached for more than a few seconds and 10 minutes would not be needed. Just wanted readers to have the correct equipment rather than assuming they could use digital based on the photo.”


Click here to read about other signs of thyroid problems and ways to improve thyroid health.

Click here to read a list of iodine-rich foods for an underactive thyroid.

This post originally appeared on My Health Maven and was written by Elisha. She is deeply passionate about educating people and empowering them to lead healthier lives. I encourage you to check out her blog

  • Hypothyroidism: The Unsuspected Illness by Broda O. Barnes M.D., Ph.D.
Elisha McFarland
Health Expert
Elisha McFarland, N.D. is the founder of My Health Maven. She turned her debilitating illness from mercury poisoning into a dedicated passion for helping people.

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