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Low Basal Body Temperature and Hypothyroidism

What does a low basal body temperature have to do with your thyroid?
Low Basal Body Temperature and Hypothyroidism
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When diagnosing someone with hypothyroidism, doctors and healthcare professionals generally look at clinical signs and changes in thyroid hormone production on a blood test. Common symptoms of hypothyroidism -- an underactive thyroid -- are assessed, such as intolerance to cold temperatures, dry skin and hair, menstrual issues, fatigue, unwanted weight gain, and depression. In addition, doctors include a complete blood test panel measuring thyroid levels –  including thyroid hormones T4 and T3 – to evaluate whether you have a thyroid condition.

Some experts believe that measuring a woman’s basal body temperature over time is a valuable way to monitor thyroid function, as unusually high or low temperatures may indicate problems with thyroid function. In this article, we’ll look at the link between a low basal body temperature and hypothyroidism. 

What is basal body temperature?

Basal body temperature is the lowest temperature a woman’s body reaches in a 24-hour period, usually when sleeping or first thing in the morning while still at rest. The basal body temperature indicates how well your body’s metabolism is running.  

This measurement is done first thing in the morning, before moving or talking, as any activity can affect your results.

The basal body temperature thermometer differs from a standard thermometer because it shows two decimal places. A regular thermometer only shows one decimal place, for example, 98.1 degrees Fahrenheit versus 98.15 degrees Fahrenheit.

A temperature reading of 96 to 98 degrees Fahrenheit (35.5 to 36.6 Celsius) is typical before ovulation in women. After ovulation, women’s basal temperature can rise to 97 to 99 degrees Fahrenheit (36.1 to 37.2 Celsius). (Note: There is no average basal body temperature for men, as it’s a term used to describe the temperature of a woman’s body at rest.)

Basal body temperature monitoring is most commonly used to assess a woman’s menstrual cycles, including ovulation, luteal phase, and menstruation. Monitoring basal body temperature is often used to help determine fertility, pinpoint ovulation, and target optimal conception times to achieve pregnancy. 

If your basal body temperature is consistently lower than expected, it could also be a sign of hypometabolism – an underactive metabolism most commonly caused by hypothyroidism. 

What is the connection between basal body temperature and your thyroid?

Thyroxine, also known as T4, is the storage form of thyroid hormone before it is converted into active T3. The level of T4 in your blood can indicate whether you have thyroid disease. T4 and body temperature can also help assess whether someone is in a hyperthyroid or hypothyroid state.

Because T4 helps to dilate blood vessels, it affects the body’s basal temperature. When too much T4 thyroxine is present in the bloodstream (hyperthyroidism), basal body temperature typically increases. A clinical sign of this is when a person feels too hot, even in a colder environment.

When T4 levels are too low (hypothyroidism), basal body temperature decreases, leading to feeling cold despite a warmer environment.

Most doctors don’t rely solely on basal body temperature measurement to diagnose or treat hypothyroidism. Still, some physicians, including Dr. Denis Wilson MD, author of Evidence-Based Approach to Restoring Thyroid Health, believe that measuring basal body temperature to assess thyroid health is potentially more reliable than blood tests alone. While Dr. Wilson’s position is controversial, some physicians include basal body temperature tracking along with the standard thyroid blood tests as part of their evaluation and monitoring. 

How to measure your basal body temperature

To measure your basal body temperature, use a specific thermometer measuring up to 2 decimal places. You can purchase one of these thermometers at any pharmacy or drugstore or even order one online. Here are five things to keep in mind to effectively monitor your basal temperature: 

1) Take your temperature as soon as you wake up while you’re still in bed

2) Keep your thermometer at your bedside table and at arm’s reach to limit the amount of physical movement (which can alter the temperature reading)

3) Ideally, take your temperature at the same time each morning

4) Factors that will influence your body temperature include: alcohol the night before, stress, traveling between different time zones, and having a cold or flu

5) Track your temperature in your notes and let your doctor know if you notice a trend, such as consistent low temperatures or consistent high temperatures

What if your basal body temperature is low?

So what can be done if you have low basal body temperature? Treatment for this condition depends on the underlying cause. When it’s due to hypothyroidism, your thyroid hormone replacement medication should help regulate your hormones and improve your metabolic rate,  naturally raising the basal temperature. 

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A note from Paloma

If your basal body temperature is constantly measuring below the norm, it could indicate that you’re not producing enough body heat or energy needed for your cells. While measuring basal body temperature is not the gold standard for assessing the presence of thyroid dysfunction, it can be helpful when used in conjunction with a complete panel testing your thyroid hormone levels (such as Paloma Health’s complete thyroid blood test kit) and tracking any physical symptoms. These tools offer a comprehensive way to evaluate and support your thyroid health and healing.

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Tracking Your Basal Body Temperature May Reveal Undiagnosed Hypothyroid. www.tempdrop.com. Accessed July 10, 2023. https://www.tempdrop.com/blogs/blog/tracking-your-temp-could-uncover-undiagnosed-hypothyroidism

Gustafson C., Denis Wilson, MD: Low Body Temperature as an Indicator for Poor Expression of Thyroid Hormone. Integrative Medicine: A Clinician’s Journal. 2015;14(3):24-28. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4566469/

Basal Body Temperature: Family Planning Method. Cleveland Clinic. Accessed July 10, 2023. https://my.clevelandclinic.org/health/treatments/21065-basal-body-temperature#:~:text=Your%20basal%20body%20temperature%20is

‌Thyroxine (T4) Test: MedlinePlus Medical Test. medlineplus.gov. https://medlineplus.gov/lab-tests/thyroxine-t4-test/#:~:text=Thyroxine%2C%20also%20known%20as%20T4

Kanagaratnam MR. Thyroid Temperature Chart & Understanding Thyroid Status. careclinic.io. https://careclinic.io/thyroid-temperature-chart/

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Neeyaz Zolfaghari

Holistic Nutritionist and Nourishment Coach

Neeyaz is a Holistic Nutritionist and Nourishment Coach. Her philosophy is built around nurturing your inner home, to transform your outer home. After learning how to heal from an autoimmune thyroid disease, Neeyaz was inspired and moved by her own journey and chose to take this self love into a business built around supporting others throughout their healing journey. Find her online at www.unspokennutrition.com.

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