B.B.T. CHARTS
Basal Body Temperature (BBT) Charting & Menstrual Cycle Tracking
Charting your menstrual cycle using basal body temperature (BBT) is a simple, low-cost and informative way to understand your hormones, ovulation and overall cycle health.
BBT charting can be helpful whether you are:
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trying to conceive
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avoiding pregnancy
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navigating irregular cycles
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experiencing period pain, short cycles, amenorrhoea or anovulation
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wanting deeper insight into your hormonal health
When tracked correctly, BBT provides valuable information about if and when ovulation has occurred and how well the second half of your cycle (the luteal phase) is being supported.
What is basal body temperature (BBT)?
When you are fully relaxed or asleep, your core body temperature lowers. This lowest resting temperature is known as your basal body temperature.
After ovulation, progesterone is released by the corpus luteum. Progesterone has a warming effect on the body, causing a measurable rise in basal body temperature. By tracking this shift over time, we can confirm whether ovulation has occurred and assess cycle patterns.
How to measure your basal body temperature correctly
For BBT charting to be useful, consistency is key.
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Measure your temperature first thing in the morning
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After at least 3–4 hours of uninterrupted sleep
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Before getting out of bed, talking, eating or using the bathroom
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Ideally at the same time each day
Research suggests basal temperature may rise by approximately 0.09°C for each hour waking is delayed, which is why timing matters.
Use a double-decimal thermometer and place it:
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under the tongue (most common)
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vaginally or rectally if oral readings are erratic (less convenient, rarely needed)
Record your temperature immediately on a paper chart or a charting app.
I commonly recommend Kindara, as it allows PDF export of charts for clinical review.
Why chart your menstrual cycle using BBT?
BBT charting gives us a month-by-month picture of what is happening hormonally.
It helps to:
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confirm whether ovulation has occurred
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assess the length and strength of the luteal phase
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identify cycle irregularities
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support fertility awareness
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guide personalised Chinese medicine and acupuncture treatment
BBT does not predict fertile days — cervical fluid does that — but it confirms ovulation retrospectively, which is essential for understanding cycle health.
Understanding a bi-phasic menstrual cycle
A healthy ovulatory cycle is typically bi-phasic, meaning it has two temperature phases:
Follicular phase (pre-ovulation)
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Lower temperatures
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Commonly around 36.1°C–36.4°C
Luteal phase (post-ovulation)
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Sustained temperature rise
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Typically 36.5°C–36.8°C
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Caused by progesterone
Ovulation usually occurs the day before the sustained temperature rise, often alongside a brief temperature dip associated with the luteinising hormone (LH) surge.
If the luteal phase is too short or temperatures are consistently low, this may impact fertility and cycle regularity.
Other signs to track alongside BBT
BBT is most useful when combined with other fertility signs, including:
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Cervical mucus changes
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Cervical position
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Breast tenderness or swelling
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Abdominal bloating or discomfort
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Changes in sleep, mood or appetite
Lifestyle factors such as stress, illness, alcohol, poor sleep or travel can also affect readings and should be noted on your chart.
Cervical mucus and fertility awareness
Cervical mucus is the primary indicator of fertility.
As oestrogen rises:
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mucus becomes clearer, wetter and more slippery
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this fertile mucus supports sperm survival and movement
After ovulation, progesterone produces thicker, drier mucus that forms a barrier to sperm.
There are several types of fertile mucus, each serving a role. For charting purposes, simply noticing when mucus becomes slippery or stretchy is often sufficient.
How BBT charting supports fertility and cycle health
BBT charting is a valuable, cost-effective tool that:
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supports fertility awareness
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assists those struggling to conceive
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provides insight into hormonal balance
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helps guide treatment strategies
While it can be used to avoid fertile windows, it does not replace safe sexual practices.
Clinical support with BBT charting
When reviewed by a trained practitioner, BBT charts can provide meaningful insight into hormonal patterns and underlying imbalances.
If you would like guidance interpreting your charts or support with cycle health or fertility, we are here to help.
📄 Downloadable BBT charts are available below.
References:
Royston J, Abrams R, Higgins M, Flynn A. THE ADJUSTMENT OF BASAL BODY TEMPERATURE MEASUREMENTS TO ALLOW FOR TIME OF WAKING. BJOG: An International Journal of Obstetrics and Gynaecology. 1980;87(12):1123-1127.
Barron, Mary Lee and Fehring, Richard, "Basal Body Temperature Assessment: Is It Useful to Couples Seeking Pregnancy?" (2005). College of Nursing Faculty Research and Publications. 6. https://epublications.marquette.edu/nursing_fac/6
Billings, E., Brown, J., Billings, J., & Burger, H. (1972). SYMPTOMS AND HORMONAL CHANGES ACCOMPANYING OVULATION. The Lancet, 299(7745), 282–284. https://doi.org/10.1016/s0140-6736(72)90291-7