How to Test Your Thyroid Function at Home


Test Your Thyroid Function at Home

Over 27 million Americans have some form of thyroid disease.  Unfortunately, a whopping 60% do not even know they have this condition.  This is because most doctors are not testing for it or they are not doing the full thyroid panel that is necessary to diagnose a thyroid condition.  In this article, I will show you how to test your thyroid function at home for free.

If you are a woman, you have a 75% greater risk of developing a thyroid problem than if you are a man!  80% of these thyroid conditions are thought to be autoimmune in nature, where the body’s immune system is attacking the thyroid tissue (1).

Unfortunately, most people struggle with poor thyroid hormone expression and are never properly diagnosed or treated to improve their quality of life and overall functionality.  The purpose of this article is to give you an easy to perform home test you can do to tip off a possible thyroid problem and get the proper testing from your doctor.


Thyroid Hormone and Body Temperature

Thyroid hormone plays a major role in the metabolism of every cell of the body.  It helps to increase the metabolic activity of the vast majority of cells and helps to regulate the body’s temperature levels.  When thyroid hormone expression is dysregulated, body temperature will be altered.

In addition, the individual may experience a number of other unwanted symptoms such as unexplained weight gain, menstrual or fertility problems, fatigue, dry skin and hair, high cholesterol and more.  I go over these symptoms in detail in this article.


Basal Body Temperature (BBT)

One of the major clinical signs of hypothyroidism is low body temperature.  Analyzing the bodies basal body temperature (BBT) through axillary (underarm) testing is a fantastic way to assess your thyroid function in a low-cost, non-invasive way.

This test was popularized by Dr Broda Barnes MD, and has been used by many medical and natural health care practitioners over the years (2).  Some research has been doing on BBT, showing that it is highly correlated with low thyroid activity (3)

While most people are aware that the standard body temperature is 98.6 degrees F, the normal underarm temperature is 97.8-98.2 deg F or 36.6-37 deg C.  If your temperature is consistently under 97.4 deg F or 36.5 deg C, then you most likely have under functioning thyroid activity.  If the temperature is consistently above 99 degrees than you may have hyperactive thyroid activity.

The Importance of Basal Body Temperature

Low body temperature is not only an indication of a possible thyroid or adrenal dysfunction, but it can also create an environment for worsening problems.  Our body temperature is critical for optimal immune function, circulation, enzyme activity and more (4).

A lower than normal body temperature creates an environment that is ripe for pathogens like bacteria and viruses.  The reason we create a high temperature fever when we have a bacterial infection or a flu is that the high temperature is inhospitable for the bacteria and viruses and it activates powerful immune activities within the body.

Additionally, enzymes are temperature dependent and won’t function well at lower than optimal temperature ranges.  A low-body temp will reduce overall enzyme activity which slows the bodies intracellular metabolism and causes an inability to buffer oxidative stress effectively.  It also leads to poor digestion and sluggish gut and liver metabolism and an inability to deactivate and excrete toxins from the body.


Instructions for The Basal Body Temp

  1. Get an old-fashioned mercury thermometer or Galinstan and put it by your bedside.
  2. Shake it down to 95 degrees F (35 degrees C).
  3. Upon arising in the morning, before you get out of bed or eat or drink anything, put the thermometer deep in your armpit for 10 minutes and record the temperature.  Be sure to place it against your skin with the tip facing up into the armpit region.
  4. This process allows you to measure your lowest temperature of the day.
  5. The temperature should be taken for 4 consecutive days.

*If you are using an oral thermometer in the mouth for this, you must realize that the oral temp is typically about a ½ degree higher.  So be sure to subtract ½ degree from your result to make it closer to your underarm temperature. If using the Galinstan or mercury thermometer in your mouth…leave it in for 5 minutes.


Menstrual Cycle and BBT

Since women are 75% more likely to have a thyroid problem, we should obviously address the role of menstruation in the BBT reading.  If you are menstruating, your temperature will naturally be higher during ovulation as it makes the egg more fertile.  This increase in temperature will skew the results.

For this reason, menstruating women should not take the test during ovulation but instead should begin on the 2nd day of menstruation and should never get closer to 4 days pre-ovulation for accurate readings.


Other Factors Involved in BBT Readings

If you have an infection or a fever, do not take the test as your temperature will naturally be skewed.  Infections and fevers drive up body temperature and may cause a false negative.  If you notice the temperature going up and down…with large gaps between days it is a sign of adrenal hormone dysregulation.

As you age, the temperature may be lower which could definitely have to do with the thyroid, but confirmative blood testing is always the best way to know for sure.  If your temperature is high, yet you have hypothyroid symptoms or have been diagnosed with hypothyroidism it may be a sign of Hashimoto’s thyroiditis or autoimmunity against your thyroid.

In autoimmune based hypothyroidism, at times thyroid hormones can range and there is an increased amount of inflammation within the body.  Both of these mechanisms can raise the BTT.  High temperatures can also be a sign of anemia or low estrogen levels.


Confirmation Testing

As a functional health doctor, I do not use the BBT as a definitive test for thyroid function.  But it can be a helpful pre-assessment.  There are other factors that will impact the BBT, such as:

  1. Active Infection in the Body
  2. Ovulation
  3. Getting up and moving in the morning before testing
  4. Adrenal Function – low adrenal output can lead to low temperature while high adrenal output can increase the temperature.

This is why I would follow up the testing with lab testing.  In particular, be sure to test all the thyroid markers including TSH, T4, T3, free T4, free T3, reverse T3, TPO antibodies and TG antibodies.  We have all of these tests and much more in our Total Thyroid panel.   We explain these tests in detail in this article.


Using the BTT for Thyroid and Adrenals

An individual can use this test to help them find out about their thyroid function as well as adrenals.  In fact, you can see how your supplement or medication dosage is supporting your body.  Here are 5 ways this test can benefit your treatment

  • After several days of taking a thyroid medication or thyroid glandular, you should begin noticing an improvement in the temperature.
  • It can help you change the dosage of your thyroid medication or supplement.
  • It can help you assess your adrenal function, which plays a role in the basal temperature as well.  This is most notable in phase IIIA-IIID adrenal dysfunction.
  • It can help you change the dosage of your adrenal supplements based on the results you are getting.


Using BTT to Look at Adrenal Function

The adrenals work to increase blood flow throughout the body as cortisol works with its cousin aldosterone, which are both made in the adrenal cortex.  Cortisol helps to maintain blood sugar, while aldosterone helps to retain sodium and maintain blood pressure.  When we retain more sodium, we also retain more water, which increases blood volume and blood pressure.  When we retain less sodium, we also retain less water, which decreases blood volume and blood pressure.

When people have hypertension or high blood pressure, they often take an aldosterone converting enzyme inhibitor (ACE inhibitor) to lower aldosterone levels and therefore lower blood pressure.  When the signaling process in the body, called the hypothalamic-pituitary-adrenal (HPA) axis is dysregulated, we can end up with either high or low cortisol/aldosterone levels.

Low blood pressure (under 100 systolic and 60 diastolic) is a common symptom for an individual with low cortisol, while high blood pressure (over 140 systolic and 100 diastolic) is common for individuals with high cortisol.  Other symptoms associated with HPA or adrenal dysfunction I discuss in detail in this article.


Testing Your Adrenals with BTT

The way most people experience low morning cortisol would be in an inability to get out of bed.  It just seems so hard to drag yourself out of bed.  If this is the case, it is most likely a low functional HPA axis in the morning.

To test your BTT to analyze cortisol levels throughout the day, follow the following strategy:

  1. 3 Hours after waking
  2. 3 Hours after that (6 hours after waking)
  3. 3 Hours after that (9 hours after waking)
  4. Take these 3 temperatures and add them up and divide by 3 to get your daily average temperature (DATS).
  5. Do this for 5 days and analyze the results of each day. If any of the days temps are more than .2F (or .1C) off from another, it may be a sign of adrenal dysfunction.

We don’t want to test in the evening or at night because cortisol should normally be low at that stage.  Cortisol should be at its highest in the morning and slowly taper down as the day goes on.

If you are using a new adrenal supplement, give it 5 days before you begin testing to give it time to work on the HPA axis before doing a 5 day DATS.  Some other home tests you could do to test your adrenal function include static blood pressure, orthostatic blood pressure and the pupillary constriction test.  I explain these in great detail in this article.


What is the Best Thermometer to Use?

Most specialists believe that the digital thermometers are not accurate enough and the temp range can vary significantly.  It is recommended to use the old-fashioned mercury thermometer.  The downside of a mercury thermometer is that if it were to break, toxic mercury vapor would be released.

I recommend a Galinstan, which is a liquid non-mercury thermometer that has a great degree of accuracy.  If you are going to use a digital thermometer, this one seems to have the best reviews.

With the Galinstan or mercury thermometer, be sure to shake it down to 95F/35C degrees the night before checking or if doing the adrenal test, right before testing.  Be sure to hold it under your armpit for a full 10 minutes before checking.

While the temperature is recording, you could read a book or website, listen to light music or watch a video.  Be sure not to move around other than the lightest of movements as needed.  For ways to improve thyroid function, read this article and if you are looking to improve adrenal function than you will want to read this article.


Sources For This Article:

1. Prummel MF, Strieder T, Wiersinga WM. The environment and autoimmune thyroid diseases. Eur J Endocrinol. 2004 May;150(5):605-18. PMID: 15132715
2. Hypothyroidism: The Unsuspected Illness com
3. Sehnert KW, Croft AC. Basal metabolic temperature vs. laboratory assessment in “posttraumatic hypothyroidism”. J Manipulative Physiol Ther. 1996 Jan;19(1):6-12. PMID: 8903695
4. Ruiz MN, García JM, Fernández BM. [Body temperature and its importance as a vital constant]. Rev Enferm. 2009 Sep;32(9):44-52. Review. Spanish. PubMed PMID: 19839238


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