Written by Nathalie Daudet

Before tracking our cycles, the only time most of us would have to pull out a thermometer is when we or someone in our life had a fever! But for many people, that's really changing. Because more and more people are taking control of their health.

An Introduction to Basal Body Temperature

Basal body temperature, or BBT for short, is the measure of your body's resting temperature. BBT can tell you a whole lot about your body and cycles because depending on which hormone is dominant (estrogen or progesterone), your resting temperature will change. Isn't that cool?

In the follicular phase of the cycle, the time before ovulation, BBT remains lower. Then, after ovulation you enter the luteal phase and BBT rises (relative to the follicular phase). This is because estrogen inhibits heat-retaining functions in the body, and progesterone has a thermogenic effect. Together, there is a noticeable shift, as you can see in the following chart.

While the only way to pinpoint exactly when ovulation happened is through a very well-timed ultrasound, BBT can get us pretty close to the time ovulation happened, within a day or two after it has happened. Knowing this, we can qualify BBT as a retrospective marker of ovulation, or one we can observe after the fact.

While ovulation can be confirmed after the fact with BBT, there's no way with just BBT to predict ovulation. Using other signs, like cervical mucus, can help you know when ovulation is approaching.

Tracking BBT for Conception

You may have heard of folks tracking their cycles in order to time intercourse if they are wanting to conceive. As women we are only able to get pregnant from intercourse during about 3-6 days per cycle! This is not a long period of time! Consider someone who's been trying to get pregnant and hasn’t tracked their cycles and identified ovulation - they may be completely in the dark as to when they can reasonably conceive in the cycle.

Tracking your BBT when trying to get pregnant can let you know

if you are ovulating (which you need to do in order to make a baby!), and
when that takes place in your unique cycle.

Contrary to popular belief, not everyone ovulates on day 14. And not all cycles are 28 days! Your cycle is unique to YOU, and tracking ovulation with BBT means you can increase your chances of timing intercourse correctly to get pregnant.

How to Track Ovulation with BBT

In order to track your BBT to find ovulation you will need:

To track your cycle on paper or in an app that has BBT tracking. The Tempdrop app will allow you to do just this!
A basal body thermometer, such as a Tempdrop. A basal body thermometer is not the same as a fever thermometer! It is more sensitive and goes up to 2 decimal places. Tempdrop specifically makes tracking your BBT simpler and more accurate than ever before.
Track your BBT daily and, if using an oral thermometer, take it at the same time every day before getting out of bed, after at least three hours of sleep. With Tempdrop, which is a wearable thermometer, you’re able to skip this step and you won’t need to wake up to take your temperature. Just turn it on before you go to bed.
Watch for a sustained shift of at least 0.2C/0.4F above the previous six temperatures that stays high for at least three days. There are more nuances to this, which I encourage you to seek help from an instructor or other resource if you are finding this part confusing! Tempdrop has a free guide to help you start learning Fertility Awareness that I highly recommend downloading for a more nuanced guide to ovulation tracking.

So what do you think? Are you ready to step into the world of tracking ovulation with BBT? Grab a Tempdrop and get going!

Nathalie Daudet is a social worker and FEMM instructor based in Winnipeg, Canada. She discovered fertility awareness after searching high and low for a non-hormonal method of birth control. After learning the magic of fertility awareness and the gift of body literacy, she decided to pursue formal fertility awareness training and share the knowledge of fertility awareness with women looking for a natural birth control option. Fertility Awareness Project is the hub for Nathalie’s FEMM classes in both group and individual formats, online and in person in Winnipeg. If you love this post and would like to thank Nathalie, shop Tempdrop with Nathalie's unique referral link.