How to Check Your Thyroid Function At Home

While health professionals continue to debate the most meaningful blood test for thyroid function, there’s one test you can do right now, at home.

This low-tech no-cost method has been around for years and serves as an excellent starting point for any discussion with your doctor about your thyroid.

Your doctor may dismiss it as not being scientifically tested, or being old-fashioned. Both are correct. The details of the test were first published in the Journal of the American Medical Association back in 1942, so it’s certainly not a “modern” test. Nonetheless, it’s served thousands of health practitioners over 6 decades as a screening tool, and it has been widely reported that the results correlate strongly with blood tests.)

The test was discovered by Broda Barnes, an American physician—born in a log cabin in Missouri, no less—who studied endocrine dysfunction with an emphasis on hypothyroidism (low thyroid function). Barnes may have been a small-town boy but he was no country bumpkin when it came to credentials. He earned a Masters in physiological chemistry from Western Reserve, a PhD from the University of Chicago, and then went on to become an MD (completing his degree in 1937). The test he invented is known as the Barnes Basal Temperature Test.

Barnes’ belief was that you could get a good idea of your basal metabolic rate (a good indicator of thyroid condition) by taking your temperature in the proper way, and using his guide to interpret the results.

It’s the easiest thing in the world to do.

  1. Get a regular mercury thermometer OR one of the newer BBT (basal body temperature) thermometers. If you use a mercury thermometer be sure to shake it down before going to bed and leave it right near your bedside.
  2. Immediately upon awakening put the thermometer under your left armpit and leave it there for ten full minutes.
  3. Note the temperature.
  4. Repeat for three to five days and take the average. (Barnes originally recommended ten days, which is probably even more accurate.)

Men can take the test anytime, but women who are menstruating should not take it during the first few days of their period. (Some say you can start taking it on the third day, some say on the fifth.)

Interpretation is easy:

  • An average basal temperature of 97.8- 98.2 is normal.
  • Anything less is a possible indicator of underactive thyroid, particularly anything under 97.6. Some practitioners (but not all) consider anything under 98 to be a possible indicator of low thyroid function, but just about everyone agrees that 97.6 or under is a problem.

It’s very important to realize that this test is not- repeat not- infallible, and Barnes himself was the first to admit that. Thyroid function depends on many things. But as a “first response” screening test, it’s hard to beat it for cost, accuracy and convenience.

Some of my favorite resources for thyroid information are David Brownstein, MD, the book “Thyroid Power” by Richard Shames, MD, and Mary Shames, PhD, and the thyroid site run by Mary Solomon.

These experts may not agree on every detail but they all have unique and valuable perspectives that are worth checking out.