Some women are all too aware of what BBT means, especially if they are in the process of trying to conceive. I have seen fertility blogs where a woman knows more about BBT than your average PhD in Physiology. However, for those of us who encounter the concept for the first time, what the heck is it?

BBT stands for basal body temperature. Both women and men have it! It just means the lowest temperature of your body during rest. The reason why it is connected to women and pregnancy is because charting the temperature can be used to predict ovulation.

In women, ovulation usually increases the BBT by ½-1 degree Fahrenheit. Normally, women have lower temperature before ovulation and higher temperatures afterward. Why does this increase happen? It has to do with hormones. Before ovulation, there is a higher degree of estrogen present which causes lower temperatures and during ovulation, there is an increased amount of progesterone, which causes an increase. After ovulation, if there is no pregnancy, the BBT will start to drop again. The charts may look different for different women because of the difference in the amount of hormones present in their bodies. This is approximately what the pattern would look like when recorded on a chart.

Biphasic BBT Chart

Having accurate charts for the temperature can help women take charge of their fertility. If you are trying to conceive, you can see if you have regular ovulation, and if you do, when the best time to…ahem…get it on is. Or, if you are trying to avoid getting pregnant, you can try to steer clear of pregnancy-causing activity during the time of ovulation (but this method alone is not accurate enough to avoid pregnancy).

There are special thermometers for measuring BBT. The regular glass thermometers are not accurate enough to detect the small change in temperature. This is what a BBT thermometer looks like.


If you want to compare different brands of thermometers, I recommend, where you can see ratings and read reviews. If you want more information on BBT, I suggest books to supplement internet research. One good one is “What Every Woman Should Know About Fertility and Her Biological Clock” by Cara Birittieri. Also, if you are trying to conceive, acupuncture treatments can be very helpful (I will do a separate post on this soon).