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Basal Temperature Testing for Thyroid Health

Because I don't like to reinvent the wheel and I have better things to do, here is an excerpt from my book Thyroid Habits - Simple Changes to Improve Thyroid Health. (Chapter 39)


Basal Temperature Testing is the process of taking your body temperature every day for about five days to get a baseline body temperature.

Pioneer Thyroid researcher Dr. Broda Barnes saw Basal Temperature Testing as the Gold Standard for testing the thyroid. He believed that no amount of blood testing could make up for the accuracy of your temperature.

As the thyroid is our thermostat, it controls our heating and cooling, which is why hyperthyroid people tend to always be hot and hypothyroid people tend to always be cold.

Knowing your base temperature will give you a good idea of which side of the fence you are on and if you should lean on your doctor or health practitioner a little more persistently if they are saying you are fine. Another bonus of temperature testing is that if you have temperatures that fluctuate up and down on a daily basis, it tells us it is a sign of Adrenal Fatigue.


  1. This test is to be performed first thing in the morning before getting out of bed. In fact, the minute you open your eyes, reach over for your thermometer and stick it under your tongue. Don't even let your partner/husband / boyfriend etc cuddle you as that will change your temperature.

  2. Take the reading for five consecutive days, if it is just a check. Or on an ongoing basis because you are trying to get on top of things and heal your thyroid.

  3. The test is to be taken in the first 5 days of your cycle (meaning during your bleed) or anytime for non-menstruating and anytime for a male. If you are doing this on a regular basis and you are still having cycles, you will see the natural rise in temperature at the time of ovulation due to the progesterone surge. This is not to be confused with your thyroid raising its own temperature.


  • Normal temperatures are between 36.5 - 37.2 (97.0 - 99.0)

  • Temperatures indicating hypothyroid are lower than 36.5 (97.7)

  • Temperatures indicating hyperthyroid are higher than 37.4 (99.2)

Obviously, blood testing is still warranted to be able to see what's happening on all levels of the making of thyroid hormone, such as the conversion of the hormone into its usable form and then the utilisation or the ability for the activated hormone to get into the cells.

Using this method is really useful for in-between blood testing or when the blood tests and doctors say "You are normal, go away". If the temperature is not in the normal range then something is still not right. It is also useful for times of healing. When you are making an active effort to reverse your thyroid disease, you can be in danger of swinging one way or the other. For example, if you are hypothyroid and taking medication, but you remove all the chemicals and toxins from your diet, start exercising, meditating and doing all the other habits in this book, you may need less medication.

Since doctors will not test the thyroid less than four weeks (and usually it won't be tested until six weeks) as it is deemed too short an amount of time to see a difference, you may find yourself swinging into hyperthyroid which is extremely dangerous and makes you feel really unwell. Taking your temperature during these times in particular will give you a much better judgment of your medication needs. It is perhaps worth finding a practitioner or a doctor who is willing to work along these lines with you.


  • Diet - you may remove foods such as grains, soy and dairy, which could impact the amount of medication you need.

  • Lifestyle - you may start exercising after many years of being sedentary, or on the flip side, you may have had an injury or a life event that has caused you to stop exercising the way you usually do. This will impact your thyroid needs.

  • Change in Environment - This could be the temperature, say for example you are spending three months in the tropics (lucky you) when you normally live in a cold area. This will likely decrease your need for medication. Conversely, if you live in the tropics (again, lucky you) and you go for an extended snow holiday, then this may increase your need for medication.

  • Life Event - A major stress in your life will definitely alter your medication needs. Whether it is moving house, a divorce, a major project at work, exams at University, or a death in the family, your temperature will tell you if your medication needs have changed.

  • Pregnancy - It is absolutely vital that you have your thyroid levels checked very regularly throughout your pregnancy and take your temperature as well. Your baby's brain health and thyroid depends on your thyroid health, so if your doctor does not order thyroid tests and tells you it's not necessary (this happened to me) then I would recommend finding another doctor if they do not come around to your request.

You don't need a fancy thermometer. You can purchase fertility thermometers or the ear thermometers that take seconds, but I just use a quick digital one that gives me a result in less than a minute and was really cheap to purchase. The one I have also holds the result till the next time I turn it on. This ability is a great asset, because if you are in a hurry to go to the loo, or someone in bed wants to snuggle (animal, human, child, take your pick) then I don't have to faff about with writing things down. For this kind of exercise, it is really important to make it as quick and painless as possible or it really won't get done!

Hope this helps! You can download the full book below if you feel it resonates.

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