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Thyroid Check: Do It Yourself!

Thermoregulation is how mammals maintain a steady body temperature. Unlike reptiles, which have a body temperature that changes with their environment, mammals need to keep a stable warm temperature all of the time. We’re warm-blooded! In humans, the healthy range is consistently at or very close to 98.6F or 37C. It is really quite miraculous that we humans can maintain the same body temperature in so many different climates!


Body temperature is an important “vital sign”: it can tell us a lot about our health. If body temperature falls too low, we call it hypothermia. If it rises too high, it is usually a fever, in response to an infection, or heat-stroke.

Your basal body temperature (BBT) is the minimum temperature that your metabolism must maintain. Your thyroid gland sets your metabolic rate and BBT, therefore your BBT is a reflection of your thyroid function. This is why we encourage people to measure their BBT as part of a full assessment of optimal thyroid function. When BBT is low, it means metabolism has slowed down, usually due to sluggish thyroid function.

Many factors can affect your temperature throughout the day, so how can you figure out your basal body temperature? You simply take your temperature when you haven’t been doing anything but staying alive for 4-5 hours. In other words, when you wake in the morning from at least 4-5 hours of restful sleep.

The advantages of using BBT to assess your thyroid:

  • It is cheap: You only have to buy a BBT thermometer once.

  • Whereas a blood test only tells you how much thyroid hormone is in your bloodstream, the BBT reflects how much thyroid gets into your cells and triggers their metabolic function. If there is any insufficiency in your body’s ability to take up thyroid hormone into your cells, your BBT will reflect this, whereas a blood test will not.

  • You get to see trends over time.

The disadvantages:

  • It only works well when you have been resting for hours. If you toss and turn, or your partner or pet disturbs your sleep, the reading isn’t accurate.

  • You have to take it as soon as possible after waking. If you get up to go to the bathroom first thing, standing up and walking triggers your adrenal glands to kick in and again, the reading isn’t accurate. Just sitting up has an effect, so you want to have the thermometer by the bed, ready to use without sitting up to find it.


Electronic BBT thermometers aren’t considered quite as accurate as liquid thermometers, but they do a reasonable job. They have the advantage that some go “beep” when the temperature reading stabilises, so you can doze or meditate with the thermometer under your tongue, and the beep acts as a snooze alarm!


For those who want really precise readings and do get good rest before waking, a way of “shaking down” the liquid in a thermometer is to put it in a sock, with the bulb that goes in the mouth at the far end, and spin the sock, making sure you don’t hit anything with it!

What does it mean if your BBT is low? Your thyroid gland isn’t working to full capacity. People often refer to this as low thyroid. The medical term is subclinical hypothyroidism. 


What does it mean if your BBT is high? This is less common than hypothyroidism, and means that your thyroid is running high and is hyperactive.


What to do if your BBT is out of range? Take that information to a Naturopathic Doctor: we know how to help you!

What is a normal BBT?

36.5 – 36.8 degrees Celsius, or 97.8 - 98.2 degrees Fahrenheit, is considered the normal basal body temperature range for people. Your temperature will be a bit higher as you move through your day.

How to take your BBT: Place your thermometer on your bedside table. As soon as you wake, place the thermometer under your tongue and wait at least a full minute, staying as still as possible. Record your temperature for three days to get an average reading. For menstruating women, do this in the first half of your cycle: before ovulation. 

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