Basal Body Temperature

It’s that time of the month again and I don’t mean your period! It’s time for ovulation! Planning to have a baby is very exciting and knowing the optimal time to try is key to optimizing your chances of conceiving. Checking your resting temperature can be one way to determine if you have ovulated, this is known as Basal Body Temperature (BBT).

The best time to check your BBT is when you first wake up. BBT will rise after ovulation has occurred due to the increase in progesterone from the corpus luteum. BBT does not detect when ovulation will occur but will help to determine a trend month to month so that you can estimate when you will ovulate going forward.

What is basal body temperature?

Basal body temperature or BBT is your body’s temperature at rest (or just when you wake up). BBT will rise after ovulation has occurred due to the increase in progesterone from the corpus luteum. BBT does not detect when ovulation will occur but will help to determine a trend month to month so that you can estimate when you will ovulate the next month.

How will you know that you ovulated?

Ovulation occurs on the last day of the lower temperatures. The rise in temperature is about 0.2 Celsius or 0.4 Fahrenheit. When your temperature is at least 0.4 degrees higher for 3 consecutive days you can assume that ovulation occurred before the spike in temperature.

Follow these guidelines to accurately take your BBT each morning:  

1. BBT should be tested first thing upon waking. Try not to move around too much in your bed as this can affect the temperature.
2. Do not get up, sit up, walk around or go to the bathroom before taking your temperature.
3. Keep your thermometer beside your bed so that it is easily reachable in the morning.
4. Try to take your temperature the same time each morning.
5. You need to have at least 3 hours of straight sleep before taking your temperature in the morning. If you woke up during the night and walked around repeatedly it can throw off the results.
6. Record your temperature as soon as you take it. You can chart it on a graph or use a mobile app such as Fertility Friend.
7. Use an accurate thermometer. Try to find a Basal Body Thermometer that is 2 decimal places.
8. Use the same thermometer throughout the whole cycle.

To learn more about if you are ovulating please check out this article.