Basal Body Temperature (BBT): What Your Morning Temperature Reveals About Your Hormones

Basal body temperature (BBT) is your body temperature upon waking. It is the lowest temperature that your body will be at during the day (Columbia University, n.d.). Measuring your BBT can help you uncover patterns in your menstrual cycle and potential thyroid hormone imbalances.

To measure your BBT, you need to take your temperature every morning at the same time before you get out of bed. Record the reading on a graph designed for BBT tracking. Make sure the thermometer you are using can measure to tenths of a degree (Columbia University, n.d.). To get an accurate reading, you must have slept for at least 3 consecutive hours before the measurement. Other factors, such as alcohol, smoking, medications, stress, illness, sleep disruption, schedule disruptions, and bedroom environment, can all impact your BBT (Berry, 2025; Maitland, 2025). You will need to collect several months of data to begin to uncover your BBT pattern.

BBT fluctuates throughout the menstrual cycle. In the first 2 weeks, known as the follicular phase, your BBT will be lower, with an average around 97 to 97.5 degrees. Then ovulation occurs, which increases progesterone and causes a rise in BBT (Tempdrop Team, 2025). Your BBT should remain elevated, in the range of 97.5 to 98.6 (Maitland, 2025), for the duration of the luteal phase which should be 10 to 14 days. You are more likely to become pregnant on the day of ovulation and the 5 days beforehand (Columbia University, n.d.). An elevation for at least 3 days indicates that you probably ovulated (Berry, 2025). If your BBT does not rise, then it is possible that you are not ovulating, which could be due to low progesterone (Tempdrop Team, 2025). After this elevation in BBT, you may see a dip in your temperature 0 to 3 days before your period begins (Tempdrop Team, 2025). Using this information can help you predict your periods, assess your hormonal health, and improve chances of conception.

The thyroid gland regulates the body’s metabolism and directly impacts BBT. If you are experiencing a BBT that is consistently below 96.8, then it is possible that you have hypothyroidism. A BBT that is consistently above 98.4 potentially indicates hyperthyroidism (Daysy, n.d.). However, BBT cannot be used to diagnose thyroid disorders. Lab tests, including TSH, free T4, free T3, RT3, and TPOAB, should be completed if you suspect a thyroid disorder based on your BBT. 

The most effective remedies for hormonal concerns are based on personalized recommendations that are tailored to your individual needs, health conditions, and life circumstances. Consider scheduling a consultation with Renewed Hope Nutrition to receive personalized nutrition advice, supplement recommendations, natural health suggestions, and functional lab interpretations. Explore our podcast to learn more about natural health.

References:

Berry, K. (April 10, 2025). Basal Body Temperature Chart and Detecting Ovulation Guide. Mira. Retrieved from https://shop.miracare.com/blogs/resources/basal-body-temperature-how-does-it-estimate-my-ovulation

Columbia University Irving Medical Center. (n.d.). Basal Body Temperature (BBT) Tracking. Columbia University. Retrieved from https://www.columbiadoctors.org/health-library/article/basal-body-temperature-bbt-tracking/

Daysy. (n.d.). A glance at thyroid function. Daysy. Retrieved from https://daysy.me/learn-more/learn-your-cycle/glance-at-thyroid-function/

Maitland, M. (May 28, 2025). What Basal Body Temperature Can Reveal: Undiagnosed Hypothyroidism. Tempdrop. Retrieved from https://www.tempdrop.com/a/blog/conditions/tracking-your-temp-could-uncover-undiagnosed-hypothyroidism

Tempdrop Team. (August 5, 2025). Basal Body Temperature - What Can It Tell You About Your Health. Tempdrop. Retrieved from https://www.tempdrop.com/a/blog/hormone-health/basal-body-temperature-and-insights-into-your-health