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How to Measure Your BBT

When you’re trying to find out when you’re ovulating (whether that’s to help you get pregnant or simply to help you understand your cycle better), one of the most popular and reliable methods to use is to measure your BBT (Basal Body Temperature). Unlike hormone-based ovulation testing methods, it remains a useful indicator when you have a hormone condition that affects your menstrual cycle. A condition like PCOS will render the standard Ovulation Predictor Kits (OPKs) close to useless, which is cruelly ironic, as it’s if you have a condition that interferes with your ovulation that you need predictions and data more than ever!

Whilst BBT remains a good indicator of your ovulation cycle regardless of the hormonal backdrop of your body, there are still limitations to the accuracy of this method and it can be difficult to record and keep track of your daily readings. Fortunately, OvuSense is here to provide some more advice about the best methods and practices to use.

What is BBT?

Understanding just what this term means and why it’s useful is a helpful first step. BBT stands for Basal Body Temperature. This is the low, minimum temperature your body drops to during rest. While you’re asleep your metabolism slows and your body cools. Measuring this baseline temperature every day reveals small changes, which are linked to your reproductive cycle. Many people experience a small drop in temperature just before ovulation, followed by a raise in the days following, and this pattern is one of the most reliable indicators your body can give you.

It has the advantage that it’s unaffected by hormone-based conditions, so it will still give you a good, reliable result even if you’re trying to get pregnant when you have PCOS. On the other hand, it is significantly more complicated to record and understand.

From the moment you wake up, your metabolism starts to speed up, helping you become awake, alert and energetic. It also heats your body, swamping those small changes to your base temperature with activity.

An Accurate Read

To get an accurate temperature reading you need to check as soon as you wake up, before you get out of bed. If you forget or leave it too late, your core temperature may have risen to the extent that you can’t see the important data you need. If you’re not a morning person, this could be a real challenge for you!

Another limitation of the BBT method is that the majority of monitors use oral thermometers to record temperatures, but this is actually one of the least accurate methods for measuring body temperature. These thermometers tend to only detect temperatures to the nearest tenth of a degree, which can mean that subtle changes in temperature are missed and result in an accurate prediction of ovulation.


In order to solve the above issues with BBT monitoring, OvuSense has developed it's own specialised vaginal sensor, which takes your core temperature right through the night to ensure accurate readings and sidestep the risk of you forgetting in the morning. This allows you to track the changes in progesterone throughout your cycle, data which is then automatically entered into a tested algorithm within our accompanying app that turns those readings into an accurate prediction of your ovulation date with 24 hours notice!

Find out more about core temperature technology and fertility here