Tracking Basal Body Temperarue
What is Basal Body Temperature (BBT) ?
BBT is your temperature at rest. A woman’s temperature will average between 36.1°C - 36.4°C before ovulation. After ovulation temperature will rise to 36.4°C - 37°C. This rise in temperature is caused by a rise of the hormone progesterone, which occurs only after ovulation. Make sure to use a basal thermometer rather than a normal one for more specific and accurate measurements as a basal thermometer will detect very small incremental changes (2 decimal places).
What is the purpose of tracking of BBT?
Tracking BBT allows you to predict and confirm that ovulation has occurred. It also allows you to pinpoint when ovulation has happened. After tracking a few cycles, ovulation can be identified as the day before your temperature rises. This is important when planning to conceive, as a woman is most fertile the days leading up to ovulation, also known as the ‘Fertile Window’. Typically 5 days before ovulation and the day of ovulation. Understanding your fertile window can help to achieve or avoid pregnancy.
How to track BBT?
Take your temperature as soon as you wake up in the morning, before getting up (the best way is to keep your basal thermometer on your bedside table and take your temperature before sitting up out of bed)
Take your temperature at roughly the same time every morning
Ensure you’ve had at least 3 hours of sleep while laying down (getting up to use to washroom can affect your temperature measurement)
Keep track of your data by charting it on paper or by using an app (I recommend Femometer, Flo, Ovia)
This is an example of a BBT Chart.
Don’t stress about the individual numbers throughout your cycle, some fluctuations are normal. It’s more important to look at the overall patterns. In general, during the follicular phase (first day of period - ovulation) usually days 1-14, your temperature will be relatively lower. In the luteal phase (time between ovulation-next period) usually days 14-28, your temperature should rise on average. Remember, it’s normal to see day to day fluctuations as shown on this chart.
There are many ways to track your fertility in conjunction with tracking BBT. It’s always important to pay attention to the way your body feels, any symptoms that come up and noting changes in cervical mucus .
Written by Dr. Kendra Zamick, Naturopathic Doctor