How to Track Your Cycle with Basal Body Temperature and Cervical Mucus

To track your cycle with basal body temperature and cervical mucus, take your temperature first thing every morning before you get out of bed, and observe your cervical mucus each day. After ovulation your temperature rises slightly and stays raised, and before ovulation your mucus becomes clear, slippery and stretchy. Read together, these two signs, known as the symptothermal method, reveal your fertile and infertile days.

What signs does cycle tracking use?

Two signs do most of the work. Your basal body temperature, meaning your resting temperature, rises by around 0.3 degrees Celsius after ovulation and stays up until your next period, which confirms ovulation has happened. Your cervical mucus changes through the cycle, becoming wetter, clearer and more stretchy as you approach ovulation. Tracking both is more reliable than tracking either one alone.

How to track your basal body temperature

Take your temperature first thing every morning, at roughly the same time, before you get up, talk or drink anything, because any activity raises it. Use a basal thermometer that reads to two decimal places, take it the same way each day, for example under the tongue, and record the reading. Over the cycle you will see a run of lower readings, then a sustained rise of about 0.3 degrees Celsius that marks ovulation.

How to track your cervical mucus

Check your cervical mucus each day and note how it looks and feels. A common pattern is dry days just after your period, then sticky or tacky mucus, then creamy and lotion-like, and finally clear, slippery and stretchy like raw egg white, which signals peak fertility around ovulation. After ovulation it usually becomes dry or sticky again.

How to combine them to find your fertile window

The symptothermal method combines the two. Your fertile window opens when fertile-type mucus appears and closes once your temperature has clearly risen and stayed up for three days, confirming ovulation has passed. Cross-checking mucus against temperature is what makes the approach reliable, because each sign catches what the other might miss. In a large study of the symptothermal method, correct use gave 0.6 pregnancies per 100 women over 13 cycles (Frank-Herrmann et al., 2007).

Tips for accurate tracking

Track at the same time each day, get a few hours of sleep before taking your temperature, and note anything that can affect a reading such as illness, alcohol or a late night. Give yourself a few cycles to learn your own pattern, and consider learning from a certified instructor. A good app makes charting and interpreting the two signs far easier and more consistent, which is what effectiveness depends on.

How Majella helps

Majella is a cycle and fertility tracking app for women of faith who practise Natural Family Planning. It makes recording basal body temperature and cervical mucus simple, then highlights your fertile and infertile phases, with your data kept private on your own device. Cycle tracking is free, and NFP features are available on a paid plan.

Related reading: What Is Natural Family Planning? A Complete Guide and NFP vs Hormonal Birth Control: How Do They Compare?.

Frequently asked questions

How soon after ovulation does temperature rise?

Usually within a day or so of ovulation your basal body temperature rises by about 0.3 degrees Celsius and stays up until your next period. Three days of raised temperature confirms ovulation has passed.

What does fertile cervical mucus look like?

Around ovulation, fertile mucus is typically clear, slippery and stretchy, similar to raw egg white. Drier, sticky or creamy mucus usually means lower fertility.

Can I rely on temperature alone?

Temperature confirms ovulation has happened, but only after the fact, so on its own it does not warn you before your fertile days begin. Combining it with cervical mucus, which changes before ovulation, gives you earlier notice.

This article is for general education and is not medical advice. Speak with a qualified NFP instructor or healthcare professional about your individual circumstances.

References: Frank-Herrmann P, et al. The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple's sexual behaviour during the fertile time. Human Reproduction. 2007;22(5):1310-1319.