The Importance of Basal Body Temperature

When working with ladies preparing for conception, I teach them natural fertility awareness methods, including Basal Body Temperature (BBT) charting. More often than not, those ladies experiencing difficulty conceiving, who have a history of miscarriage or who present with many pre-menstrual or menstrual related symptoms, have low basal body temperatures. This can be due to slow metabolism and low thyroid function. However, this usually goes undetected for months if not years. What’s more, a thyroid blood test will often come back as ‘normal’, as the issue isn’t with the thyroid gland itself but instead with the conversion of the hormone T4 to the usable form T3, which occurs in the liver.

If the liver is not functioning optimally, this conversion won’t take place and will result in symptoms such as cold hands and feet, irregular menstruation, constipation, chronic fatigue, water retention, hypoglycaemia, thinning hair and dry skin, as well as low body temperatures.


Why is this important? Basal body temperatures reflect our metabolism and therefore how well our body systems and processes are functioning. If everything is sluggish, your reproductive and hormonal systems will not be working optimally.

The other reason we measure BBT is to monitor ovulation. Following the release of an egg, the BBT will rise slightly, as a consequence of the increased progesterone produced in this phase of the cycle. Progesterone is key to maintaining the womb lining in preparation for a developing embryo and is also responsible for heating up the body to create its own little incubator for that baby. Therefore, low temperatures will highlight low progesterone levels, which is vital to address ahead of trying to conceive.

Pre-ovulation temperatures taken first thing in the morning should be no lower than 36.4 degrees C. Post-ovulation, you want to see your temperature around 36.6-37.0 degrees C.

I have seen many women with temperatures presenting lower than 36.0 degrees C and this is not good in terms of fertility. But this can absolutely be addressed with some simple changes. Every one of my ladies who has followed these suggestions have improved their temperatures to within optimum levels.

If your temperatures are low, make sure to read next week when I’ll be sharing my top tips.