How Does BBT Work?

August 19, 2022 | By: Kacie Shrock, RN, BSN 

What You’ll Learn: 

  • BBT (Basal Body Temperature) is your body’s temperature at rest.
  • BBT rises after ovulation, thanks to the hormone progesterone.
  • Tracking your BBT allows you to confirm that ovulation occurred and better predict when you will ovulate in your next cycle.
  • BBT works best when you combine it with ovulation tests to predict ovulation

If you’re trying to conceive and have been reading up on fertility awareness and how to best track your cycles, chances are you have heard of BBT (Basal Body Temperature) tracking. BBT tracking is an accurate way to confirm that ovulation has occurred each month which we will discuss in more detail below. 

BBT can confirm your ovulation

What is BBT?

Basal body temperature (BBT) is the body’s lowest resting temperature. This temperature reading provides women with a tool to track their cycles and helps to actually confirm ovulation.

BBT should be measured upon waking up, after your body has been fully at rest for at least 3 consecutive hours, before you get out of bed, talk, eat or drink. When you track your BBT, you are able to observe subtle shifts in temperature based on where you are in your menstrual cycle. 

How Does BBT Work?

Your temperature naturally changes throughout the menstrual cycle. It is lower in the first half of the cycle and rises after ovulation due to an increase in the hormone progesterone. 

The release of an egg (ovulation), is accompanied by a release of the hormone progesterone, a reproductive hormone responsible for maintaining the early stages of a pregnancy. Progesterone increases the basal body temperature by about 0.5 - 1.0 degree shortly after ovulation, which can be noticed on your Premom chart when tracking BBT. Ovulation can be confirmed when you notice a shift in your temperatures thanks to that increase in progesterone, it’s typically observed after 6 low temperatures before ovulation, followed by 3 high temperatures after ovulation. 

A BBT chart sample to confirm an ovulation

Progesterone and body temperature will remain elevated for the remainder of the cycle, decreasing back down to baseline just before you begin your period.. A body temperature elevation that remains elevated may be a sign of pregnancy, so if you notice your temperature remains elevated as your approach your missed period, it may be time to take a pregnancy test! 

Is BBT Accurate? 

Tracking BBT can provide accurate information about your cycle and help you identify your fertile window, however there are a few factors and rules that need to be followed for best results…

  • Temperatures need to be consistent, recorded around the same time daily after at least 3 consecutive hours of sleep. 
  • Temperature should be taken immediately upon waking up, before getting out of bed, eating or drinking. 
  • Environmental factors such as illness, stress, alcohol consumption and travel can influence shifts in you BBT.
Using a Premom app to track your BBT!

Using BBT to help track your cycles is a cheap and easy to use method to help confirm that you are ovulating. Since BBT rises after ovulation, it is best to combine this method with ovulation testing kits that track luteinizing hormone and tracking cervical mucus, which both can help identify your fertile window leading up to ovulation and ovulation day, allowing you to better time sex for conception. 

Should I Track BBT Besides Ovulation Testing?

While basal body temperature tracking is a great tool to help track ovulation while trying to conceive, it can also be used just as a tool to track your overall cycle health for those who are not just TTC. Having insight into your overall cycle health can tell if you are dealing with any possible hormonal imbalances or not. The temperature will help you confirm your ovulation and could work as a great tracking method to identify your fertile window.

Have more questions about how to accurately track BBT? Submit your question to one of our Premom Experts using “Ask An Expert” in the Premom app and have your questions answered within 1 business day.

Use BBT with our Premom app together

About author


Kacie Shrock is a registered nurse who specializes in fertility and reproductive health. She has always had a passion for women's health and she supports women and couples virtually across the world while on their journey to their dream families. Schedule a consultation with Nurse Kacie right through your Premom app! 


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