Basal Body Temperature

In its daily rhythm, the human body is subject to periodic temperature fluctuations. During sleep, a temperature minimum is established in the body core, which is called body basal temperature (BBT). In practice, the core body temperature upon waking is often referred to as the BBT. 

The basal body temperature in the first half of the cycle (at the beginning of the period until ovulation) is about 36.6 °C. Shortly after ovulation, the temperature rises by at least 0.2 °C and is also slightly elevated on the following days.


Discover the fascinating nuances of your body's signals with a glimpse into different basal body temperature curves. From the 'typical' curve showcasing the rise of ovulation, to unexpected drops and rises that reveal thyroid function, this exploration unveils insights into fertility, health, and well-being.

Your body resets your temperature when you get sufficient sleep. Check your BBT chart, and you’ll see that it’s not constant but varies within a narrow range. BBT typically shows a biphasic pattern that matches the two phases of your menstrual cycle, and your hormones are responsible. Let’s walk you through the process.

American physician and professor of medicine Broda Barnes developed and promoted a diagnostic test for thyroid function in the 1970s. Discover how this traditional approach, though less common today, can provide invaluable insights into thyroid health by measuring basal body temperature.