If you have ever been hospitalized, one of the first things a nurse will do is take your temperature. This is a vital sign along with heart rate and blood pressure.

Your basal body temperature is a great representation of not only your well being but what is occurring at the cellular level. The definition of a calorie or gram calorie (usually denoted cal) is “the amount of heat energy needed to raise the temperature of one gram of water by one degree Celsius (or one kelvin).” In other words, your temperature is intimately related to your metabolism or your ability to ‘burn’ calories.

Seemingly outside the hospital this easy and affordable test is neglected compared to taking one’s blood pressure.

The body’s ability to maintain a temperature with little fluctuation is called thermoregulation. This process allows your body to maintain it’s core internal temperature. All thermoregulation mechanisms are designed to return your body to homeostasis (a state of equilibrium).

A healthy internal body temperature falls within a narrow window. The average person has a baseline temperature between 97.8° Fahrenheit (36.6° Celsius) and 100°F (37.8°C). Your body does have some flexibility with temperature. However, if it varies too much it can affect your body’s ability to function. For example, if your body temperature falls to 95°F (35°C) or lower, you have “hypothermia.” This condition can potentially lead to cardiac arrest, brain damage, or even death. If your body temperature rises as high as 107.6°F (42 °C), you can suffer brain damage or even death.

You can see with a variance of 4 degrees farenheit or 2 degrees celsius the body can be in trouble. This emphasizes just how important and telling the body temperature is.

Those who have used the temperature method to get pregnant will have some insight into the importance of body temperature. That method involves tracking the basal body temperature and trying to conceive a couple days prior to raising. A women’s body temp will raise about .5 to 1 degree about midway through cycle due to an increase in progesterone.

There are various mechanisms involved in controlling body temperature which include:

Sweating: Your sweat glands release sweat, which cools your skin as it evaporates. This helps lower your internal temperature.
Vasodilation: This happens when the blood vessels under your skin get wider. This increases blood flow to your skin where it is cooler and away from your warm inner body. This lets your body release heat through heat radiation.

If your body needs to warm up, these mechanisms include:

Vasoconstriction: This occurs when blood vessels under your skin become narrower. This decreases blood flow to your skin, retaining heat near the warm inner body. Example: cold hands, feet and possibly nose.
Thermogenesis: Your body’s muscles, organs, and brain produce heat in a variety of ways. For example, muscles can produce heat by shivering.
Hormonal thermogenesis: Your thyroid gland releases hormones to increase your metabolism. This increases the energy your body creates and the amount of heat it produces.

There are many ways to record body temperature but the three more common choices are:


The digital thermometers of today make this the preferred choice for convenience. Drinking or eating very hot or cold food can affect temperature measurement when measuring orally. 15 to 20 minutes should be a safe time frame away from food and drink. Physical activity can also alter a person’s core body temperature. If you just came off a spin bike give yourself some time to recuperate before taking a measurement. Usually exercise will drive up temperatures unless the adrenals are on overdrive. It is important that the you keep your mouth closed during oral measurements. The most accurate results will come when the thermometer is properly positioned in the sublingual pocket and the mouth is closed.


The underarm must be dry prior to measurement. You may need to wipe with a dry towel prior to measurement.
After placing the probe tip in the armpit, bring arm down close against the body to trap body heat.
The probe tip should be oriented in the same direction of the body, with the tip towards the patient’s head.

basal body temperature thyroid

Rectal Measurement

Not the popular choice, but some contend to be more accurate. Generally, water-soluble jelly or petroleum jelly should be used as a lubricant when taking rectal temperatures. This will allow for easier insertion of the probe and hopefully increase comfort during the measurement.

The probe tip should be inserted no more than ½ inches or 1.3 cm into the rectum. You should never force the probe tip in if resistance is encountered.

Keep in mind if you have been recently heavily exercising your lower body you may have an elevated rectal temperature.

In 1942, a doctor named Broda Otto Barnes made it popular to access thyroid functioning using the thermometer. He contended that a blood serum test for thyroid was not accurate and he would still see patients with good test numbers but classic hypothyroid symptoms. He discusses this in great length in his book, ‘Hypothyroidism: The Unsuspected Illness’ and continued with support in, “Solved: The Riddle of Heart Attacks.’

He argues that Basal Body Temperature (BBT) is a more accurate and a more convenient predictor of thyroid status than both Basal Metabolic Rate (BMR) and blood cholesterol. In his book he advocates oral measurements. “The patient places a thermometer and book by his bedside. When he awakens in the morning the thermometer is left in the mouth without interruption for ten minutes by the clock.” He states: “From a study of over 1,000 cases the results indicate that subnormal body temperature is a better index for thyroid therapy than the basal metabolic rate.”

At least a couple of popular studies would support this assertion.

The biosphere 2 study where healthy adults spent 2 years sealed off from the outside world. They had to eat a low-calorie diet that caused 18% weight loss in men and 10% weight loss in women. These participants were not overweight going in and had an average body temperature around 98.6. But by the time they got out, their body temperatures had dropped between 96-97 F. and sometimes lower. When they started eating again and regained their weight, their body temperature went back up to normal. This mirrored their thyroid function. A lower body temperature corresponded to lower thyroid hormone levels. Evidently, their body temperature dropped as their metabolic rate dropped. It then rebounded when they resumed their normal eating pattern.

A similar result came from the Minnesota Starvation Experiment. This 1945 study was intended to observe the physiological and psychological effects of dietary restriction and subsequent re-feeding.

The study was designed to have the participants lose 25% of their normal weight. For the first three months, participants ate 3200 calories a day and were quite well fed and comfortable.

Then, for the next six months, participants were restricted to an uncomfortable low calorie diet of 1570 calories a day. After this brutal period of deprivation, the men were then fed 2000-3000 calories a day. Finally, the study was concluded with the participants being allowed to eat an unlimited number of calories a day.

During the starvation period there were very noticeable changes.

Body temperature dropped. Heart volume dropped by 20%. Heart rate slowed. Obsessive thoughts of food. Bingeing behavior. Extreme depression. Severe emotional distress. Irritability. Loss of libido. Interest in everything other than food vanished. Social withdrawal and isolation. Several subjects became frankly neurotic. One patient reportedly amputated 3 fingers with an axe in an act of self-mutilation. WTF !

Safe to say this study won’t be repeated.

Resting metabolic rate had dropped by 40%! In other words, the body was shutting down. Let’s consider this from the body’s point of view. The body was accustomed to getting 3,200 calories per day and now it was getting 1,570. In order to preserve itself, it lowers energy production. It has no choice.

The heart gets less energy slowing the heart rate and heart volume shrinks. Blood pressure drops.

The heating system is turned down so the body feels cold.

Muscles get less energy leading to physical exhaustion.

Hair and nails get less energy resulting in hair loss and brittle nails.

These were survival measures the body used under a time of extreme stress.

Not trying to get sidetracked here but I want to show how metabolism, body temperature, energy and well being are extremely intertwined. I also want you to take notice of the calorie count in the deprivation phase of 1570 calories a day. This number and below is routinely handed out in weight loss regimes.

Broda Barnes recommended tracking temperature over a period of time (5-7 days should work) to get an idea of what was happening.

Taking your temperature upon waking before you brush your teeth or drink/eat would be the first measurement of the day. This is the measurement you’ll be at your lowest temperature likely. The body typically will rise slightly throughout the day and usually slightly after meals. Tracking for 5-7 days will give you a good picture of how your body is functioning.

A healthy functioning thyroid will consistently maintain a basal body temperature between 97.8 °F (36.6 °C) and 98.2 °F (36.8 °C) upon waking.

Anything lower than 97.8 °F (36.6 °C) implies that at complete rest, your cells are not able to produce adequate energy to meet the energy demands of your body.

low body temperature and thyroid

In Broda Barnes opinion this would indicate that you are in fact hypothyroid.

It should now be becoming apparent how thyroid is intimately linked to body temperature. Having your thyroid (TSH) checked in conjunction with body temps will give even further insight.

What to do if your temps are chronically low?

Improve Thyroid functioning. This should be an obvious one considering what we’ve discussed. Get your blood serum checked and then discuss numbers with your doctor or practitioner. Hopefully, that person is willing to listen and work with you towards improved health.

Keeping your extremities warm. It may seem peculiar wearing socks to bed or wool slippers in June but those people who are habitually cold realize just how uncomfortable this can be. Having chronically cold feet and hands is a feeling most want to avoid. This too, will be more typical during winter months.

Hot bath (epsom salts) and showers. You don’t want it to the point of being uncomfortably hot because that can bring it’s own issues.

Exercising. This doesn’t have to be intense to get temps up. Record your temperature 20-30 minutes post exercise to get a feel of what the internal climate is doing.

Increasing carbon dioxide (Co2). Greta Thunberg on line one! Not that one, but instead your concentration in your blood. Co2 levels should be in the high 20’s when looking at a blood test.This can be accomplished at least temporarily by holding our breath for extended periods. This will increase the Co2 concentration internally. Also, bag breathing which at one time was recommended for panic attacks. You could also move to a higher elevation, if you are hardcore about it. Holding your breath and bag breathing are the easiest options and you’ll see and feel immediate changes. From my experience, you’ll see increases from .5 degrees to over a full degree celsius in a few minutes.

Some foods and spices have shown effectiveness. Foods like coconut oil and spices like tumeric, cumin, and cayenne pepper have shown some effectiveness as well.

Warm and hot drinks. This shouldn’t be a surprise considering we reach for hot chocolate or coffee /tea to help regulate the system. Just the opposite of a cold drink on a hot day.

Infared saunas and/or heat lamps. Heating pads and electric blankets can be included here and can undoubtedly bring comfort to those of us ‘temperature challenged’.

For those who are running a chronically higher temperature there is a chance you are hyperthyroid. This tends to regulate over time if there isn’t something pathological as the cause. Adrenaline can also artificially inflate the numbers which is why pulse may be taken. I’ll explain this in a future post. Don’t let how you feel to necessarily give you the answer. For those women around menopause the feeling and sensation of hot flashes are actual dips in temperature. You do want to confirm with a thermometer.

Sometimes the answers we are looking for are right in front of us. Teenagers with jackets undone in the midst of winter and seniors who have the heat set on cremate enables us to see the close relationship of temperature, metabolism and healthy aging.

I discuss other ways to check metabolism plus easy home tests in my metabolism guide.


Dr Denis Wilson has a temperature reset protocol to reset the temperature though use of thyroid (T3)


Dr. Wilson’s protocol is interesting for a couple reasons. One is that he doesn’t believe you need to be on medication for the rest of your life and the body can handle thyroid production on it’s own once it’s “reset”. This is a complete 180 compared to hearing, “you’ll never come off thyroid medication.” Also, of note his recommendation of T3 ( triiodothyronine). In Canada, the most widely prescribed thyroid medication is Synthroid (Levothyroxinein the U.S.) which is T4 (thyroxine). Rarely if ever do you hear T3 being mentioned or prescribed in Canada. T4 is supposed to convert to T3 in the body unless it’s be ‘blocked’ in some way.

Thyroid medication is usually the top 2 or 3 prescribed medication in North America. If you consider those who score well on blood tests but still have symptoms (subclinical) then it’s safe to say a large group of the population have hypo symptoms.

My advice would be to get regular blood work and see if they correlate to your basal body temperature and symptoms. I would keep record of your own blood work to see where it’s trending. Doctors are busy people and previous tests may not be viewed. Be proactive with your health. It’s your body.


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