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Health Library

    What is basal body temperature, and how do you measure it?

    Updated 19 December 2023 |
    Published 01 October 2018
    Fact Checked
    Dr. Jenna Beckham
    Medically reviewed by Dr. Jenna Beckham, Obstetrician, gynecologist, and complex family planning specialist, WakeMed Health and Hospitals, Planned Parenthood South Atlantic, North Carolina, US
    Written by Kate Hollowood
    Flo Fact-Checking Standards

    Every piece of content at Flo Health adheres to the highest editorial standards for language, style, and medical accuracy. To learn what we do to deliver the best health and lifestyle insights to you, check out our content review principles.

    You might have heard that tracking your basal body temperature (BBT) can help you conceive, but is that really the case? And how do you do it? Here, a Flo expert explains everything you need to know about BBT.

    Understanding your cycle has lots of benefits, from knowing when you’re most fertile to when you might be a little crankier than usual (thanks, PMS). 

    Tracking your basal body temperature (BBT) is one of the ways you can get to know your cycle better. Your BBT increases just after ovulation, so by recording it each day for a few cycles, you can learn when you tend to ovulate. 

    But your BBT isn’t the same as your regular temperature, and you have to measure it in a certain way to get an accurate reading. Here, Flo expert Dr. Charlsie Celestine, obstetrician and gynecologist, New Jersey, US, explains exactly how to measure your BBT. She also explains how BBT tracking can indicate when ovulation happens if you’re trying to conceive — and even when you might be pregnant.

    However, it’s important to note that you should never use BBT as a method of birth control. Its effectiveness is limited as many factors can influence your body temperature, including stress and having a fever

    Key takeaways

    • Measuring BBT can help you understand when you ovulate and when your most fertile days are.
    • Your temperature rises very slightly once ovulation has happened and stays high until just before you get your period.
    • If you conceive, your temperature will remain high — so your BBT could even provide an early indication that you’re pregnant.
    • However, certain factors can impact the accuracy of your readings, like sleeplessness, illness, and drinking alcohol. That’s why you should never use BBT as a method of birth control.