How to take your Basal Body Temperature
Your Basal Body Temperature can be taken orally with a normal mercury thermometer or a basal digital thermometer. Ideally, a larger thermometer that registers from 96F to 100F / 34C to 39C degrees (in easy-to-read one-tenth degree increments) is recommended.
Important: Your BBT temperature refers to a 'resting' or 'base' temperature. That means that your BBT must be measured prior to any physical activity, after at least four hours of sleep.
1. Taking Your BBT Temperature
Take your BBT temperature first thing each morning - as soon as you wake up. You must remain in bed (as physical activity can increase your temperature) and avoid eating or drinking or even moving. Either insert the thermometer in your mouth - or alternatively your rectum - and wait five minutes. Read the temperature to within 1/10 of a degree and record the reading.
2. Charting Your BBT Temperature
Starting on day one of your menstrual cycle - the first day of your period - begin recording your BBT temperature using a calendar or notebook and graph paper. Each morning, record your temperature. Plot each day's BBT on the graph. Your temperature rise may be sudden, gradual, or in steps. The pattern may vary from cycle to cycle.
3. Predicting Ovulation, menstruation and Pregnancy
For most women, 36.2 to 36.5 degrees is considered normal prior to ovulation and 36.7 to 37.1 degrees after ovulation. By charting the differences - in one-tenth degree increments - you can determine when ovulation has taken place. Typically a rise of at least 0.4 to 0.6 degrees will take place after ovulation, though for different women the temperature increases may be sudden or gradual.
Pretty common for women who find their temperature cross 36.7 degree as the point of their ovulation day
And when your temperature drop down back to the normal range , your menstruation would start within the 24hrs. Another way of predicting your menstruation day is by adding 10 to 14 days from your ovulation day (the day when you detected a sudden increase of temperature).
18 consecutive days of ovulation high temperatures means a woman is almost certainly pregnant
recent studies show that if your BBT chart show signs of triphasic pattern (3 time of upward shift temperature within the cycle) there is sign of possible pregnant.
BBT Limitations in Ovulation Prediction
BBT charting only tells you when ovulation has already occurred - and is therefore important for predicting general patterns. To predict ovulation, LH testing (ovulation predictor kits) is more effective - and examining cervical mucus is also a very valuable method.