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Basal Body Temperature or BBT

woman lying in bed checking her basal body temperature or BBT to check fertility, infertility, progesterone production for endometriosis, fibroids
Why and how do you check your BBT?

By Dr. Pamela Frank, BSc(Hons), Naturopath

What is Basal Body Temperature?

Basal Body Temperature or BBT is your resting body temperature. It is usually checked as soon as you open your eyes in the morning. It is best taken before you get up, or move around overly much. Your thermometer should be on your night table, right beside your bed so that you don’t have to get up to go and get it. You pop it under your tongue, in your ear, or under your arm first thing each morning. Aim to check your BBT at about the same time each day, 7 days per week. You want to check your BBT throughout your entire cycle, ideally for 2 or 3 cycles. Basal body temperature should also be checked after at least 4 hours of consistent sleep.

What is the purpose of checking BBT?

As a naturopath, I will ask many of my female patients to check their BBT. There is a wealth of information that we can gather from this information.

  • Are you ovulating? Despite common misconceptions, having a regular period does not guarantee that you are ovulating. Even having a positive ovulation predictor kit test (OPK), does not guarantee that ovulation is actually occurring. The OPK tells you that your body is TRYING to ovulate, but does not confirm successful ovulation. BBT confirms whether ovulation was successful.
  • When are you ovulating? For the purposes of trying to conceive, knowing when you ovulate from your BBT will help you to time intercourse for the days when conception will be most likely to be successful.
  • Once you do ovulate, is your progesterone production healthy? The increase in progesterone that follows ovulation is what increases your body temperature post-ovulation. What we like to see on a BBT chart is a fairly abrupt rise after ovulation, and then a relatively stable temperature until just before your period is going to come. BBT charting has advantages over blood testing for this purpose. It gives us more of a broad overview of what your progesterone production is like throughout the portion of your cycle after ovulation, also known as the luteal phase. Healthy and consistent progesterone production is vital for embryo implantation and maintenance of the pregnancy. Women who struggle with infertility often have suboptimal progesterone production throughout their luteal phase. Even in women who are not trying to conceive, healthy, consistent progesterone production prevents menstrual cramps, relieves anxiety, maintains healthy bone density, and relieves conditions like endometriosis, polyps, and fibroids.

Once you have collected your BBT readings, you want to input them into an app that will transform the BBT numbers into a graph. The graph is easy to distinguish the patterns that indicate ovulation and subsequent progesterone production. The apps that I will commonly recommend to patients include Kindara and Fertility Friend. Although, if you have a favorite period tracker app already installed on your phone, it likely has a BBT function built into it.

Picture of Toronto Naturopath Doctor Dr. Pamela Frank, Best Naturopath in Toronto many times over
Dr. Pamela Frank, BSc(Hons), Naturopathic Doctor

Dr. Pamela has practiced as a naturopathic doctor in Toronto since 1999. She has received numerous “Best Naturopath in Toronto” awards. She is registered with the College of Naturopaths of Ontario.

Dr. Pamela Frank uses a natural treatment approach that may include acupuncture, herbal medicine, nutrition, diet, vitamins, supplements, and other natural remedies to restore balance and provide long-term resolution to almost any health problem.

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