How To Track Your Fertility Using Basal Body Temperature (BBT)

Nothing makes you feel more competent than understanding how fertility tracking works. Suddenly, it no longer feels like you need a second degree just to know if you’re ovulating. 

Many women (and their partners) feel more empowered and slightly more in control when they understand how menstrual cycles work in general and how theirs works specifically. 

Understanding basal body temperature, or what happens to your temperature when ovulating, won’t always be a fool-proof method for tracking your fertility because of how many external factors can impact your temperature. Still, even so, it can really help.  

So let’s start at the very beginning of the overwhelming iceberg — what is BBT, and how you can use it to track ovulation. 

What is Basal Body Temperature?

BBT stands for basal body temperature, the lowest temperature your body reaches after a period of rest. Your BBT increases or decreases ever so slightly on any given day in your menstrual cycle. A BBT thermometer differs from a traditional thermometer because of its added accuracy — it tracks the temperature to the tenth of a degree (think 98.67 instead of just 98.6). This more detailed temperature read can help you track your fertility more accurately, particularly since changes in basal body temperature are usually very slight (like four-tenths of one degree, according to Planned Parenthood).  

Women can use the BBT method to track their ovulation when trying to conceive or as a form of natural birth control, commonly known as the “fertility awareness method.”

When you ovulate, your temperature rises due to an increase in the hormone progesterone. Then, just before your period starts, progesterone levels drop. This means your basal body temperature will drop, too. If your temperature remains high, it may be time to take a pregnancy test! 

What impacts your BBT? 

According to Planned Parenthood, you’ll want to track your BBT for at least three months before using it as a reference for your menstrual cycle. This is because many things can shift your temperature up and down that would be hard to spot across just one month of data. 

For instance, menstrual conditions like PCOS or endometriosis may make it harder for some women to use the BBT method to track fertility because of their irregular periods. 

Studies found that factors like stress, getting sick, or even sleeping less or drinking more alcohol can also impact your BBT.  

How do you measure your BBT?

Before we dive into what technology you can use to track your BBT, it’s important to know how you should track your BBT in the first place. 

According to Planned Parenthood, all of these factors are important when tracking your basal body temperature: 

• Take your temperature first thing in the morning before you do anything else

• Take your temperature every day

• Exclude your temperature if you are sick, slept differently, or have had alcohol, for instance 

Can certain tech, like the Apple Watch, help you track your basal body temperature? 

We have entered the modern age of BBT tracking, which means how you track your BBT is a personal choice (and sometimes even a fashion choice).

Wearables like the Apple Watch and Oura Ring can now track your basal body temperature while you sleep. The Oura Ring also syncs directly to Natural Cycles, the first FDA-approved birth control app, which helps chart your cycle and points out your fertile and non-fertile days. 

Natural Cycles also works without the Oura Ring. The app has a basal body thermometer that is included with your yearly subscription and syncs automatically with the app once you take your temperature. While wearable tech takes the guesswork out of remembering to take your temperature every morning, Natural Cycles’ thermometer can still be an easy user experience.

It’s true that apps are bridging the gap for those who love technology, but tracking your BBT without ever downloading anything onto your phone is possible. Basal body thermometers are sold at major retailers (both online and in person), and you can use BBT tracking graphs to track your temperature and cycle manually. Planned Parenthood offers an example on its site.

No matter how you track your ovulation, the most important thing is that it’s something you’re comfortable keeping up with daily — since daily measurements are what will help you better understand your cycle and its trends. And there's no better feeling than that.