Whenever I have a woman who comes to me who is having trouble conceiving, I ask them if they have been charting their basal body temperature, or BBT. Many women I see have, at some point, charted their BBT, but gave up after a few months because it was just “ONE MORE thing to do” when working on fertility. It is true, that charting your BBT may not be the very best predictor of ovulation. However, it does give me, as a practitioner, good information as to what may or may not be going on in the body at different phases of a woman’s cycle. BBT tracking for fertility is also recommended by experts such as WebMD.

There are four phases to a woman’s cycle: Menstruation, Follicular, Ovulation, and Luteal.

Menstrual Phase: Considered Day 1 of your cycle. This is when menstruation occurs. This phase is when the products of the previous cycle are excreted from the body so that a new cycle can begin.

Follicular Phase: Starts around day 4 or 5. This is when a follicle is recruited from the ovary, and develops into a mature egg. Body temperatures should be in the range of 97.2 to 97.6 degrees Fahrenheit. The temperature should be fairly stable, with a fluctuation of 0.2 to 0.3 degrees.

Ovulation: Occurs at mid-cycle, typically around day 14. This is when the mature egg is released. Your temperature should ideally spike 0.5 to 1.0 degrees Fahrenheit over a 1-2 day period.

Luteal: This is when the fertilized egg travels down the fallopian tube to implant into the uterus. The body temperature should be in the range of 97.8 to 98.4 degrees Fahrenheit. Temperatures should be stable, with fluctuations of  0.1 to 0.2 degrees. If pregnant, you may see another increase in temperature around day 21.


The day and temperature ranges are based on an ideal 28 day cycle with no other health issues. If there are anomalies, it can tell me where the problem may lie, and how to treat it. For example, if temperatures in the Follicular phase are too low, maybe there is a problem with a low functioning thyroid. If I don’t see a good spike in temperature with ovulation, maybe there was a poorly developed follicle, and I have to try to increase the nutrients to the egg in the next cycle. Temperatures that are all over the place with no consistent pattern can be an indicator of PCOS.

If you do choose to chart your BBT, here are some tips:

1.Get a BBT specific thermometer. They are more sensitive than regular thermometers, and are generally accurate to the 1/100 degree. It doesn’t have to be expensive. Any good BBT thermometer will be adequate, unless you specifically want more features, such as being able to sync to your smart phone.

2.Take your temperature as close to the same time as possible each morning. Do this before getting out of bed or going to the bathroom. Even a 30 minute difference in time can affect your temperature

3. Make a note of how well you slept the night before, or if you consumed any alcohol. This can also affect your        temperature.

4. Decide on how you want to take your temperature and be consistent with it. You can take your temperature vaginally, which is more accurate and will give you more consistent results, or you can take it orally, which is much easier, but will give you more temperature variations.


If you would like to learn more about charting your BBT, or if you have any other questions or concerns regarding your fertility, please call the office to schedule a free consultation appointment.