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How to Chart Your BBT
- Purchase a Basal Body Temperature (BBT) thermometer. You can get one at your local drugstore or in our RESOURCES center. A BBT thermometer is preferred because it records your temperature to the tenth degree and is the most precise thermometer available.
- Get some graph paper or set up an excel spreadsheet in order to record your daily temperatures.
- Have your chart, pen and thermometer handy. Most women keep their BBT supplies beside their bed at night. It is important that you take your temperature while you body is at rest so you don’t want to have to get out of bed to look for your supplies.
- Start charting on the first day of your menstrual cycle, which is also known as “cycle day one.”
- Take your temperature at the same time everyday. You may want to set your alarm clock to wake you up at the same time each morning.
- Make sure you have been asleep for at least three hours before you take your temperature. In fact, five hours of sleep is even better. If this isn’t the case, still take your temperature, but note this on your chart.
- Don’t drink, eat or smoke before taking your temperature. You want to take your temperature first thing after you wake up before you have done anything!
- Take your temperature consistently. While you can take your temperature orally, rectally, or vaginally, make sure you do it the same way each time.
- Once you have taken your temperature, record it on your chart each day. Try not to read too much into any one reading until your cycle is completely over.
- Look at the chart at the end of the month to analyze what happened to your body temperature. It may take a few months to identify any patterns. What you are looking for is a 0.4 degree Fahrenheit increase over a 48-hour period which indicates that you have ovulated.
- What if you oversleep or forget to write something down? Don’t worry. The overall goal of BBT charting is for you to get a better idea as to your ovulation cycle. It’s not an exact science. If you forget something, just make a note of it on your chart to jog your memory when you go back and review it.
- Consider drawing a coverline. While this isn’t necessary for charting your BBT, many women find it helpful because it will help you better visualize the two phases of your menstrual cycle — the follicular and luteal phases.
How Do I Draw a Coverline?
The easiest way to draw a coverline is to look at the six days before you ovulate. Take the highest temperature over these six days and draw a horizontal line one-tenth of a degree higher than your highest temperature. Notice how the temperatures before ovulation are lower than your coverline and the temperatures after ovulation are higher.
After ovulation has occurred, your temperatures should stay above the coverline for about 12 days. If your temperatures fall below the coverline during this time, this might indicate a short luteal phase or a luteal phase defect.
What Else Should I Include on My BBT Chart?
The information contained on your BBT chart will help you better understand what's going on with your body. Any additional information that you can provide will not only help you, but will also assist your health care provider in determining what is going on.
Many women include all signs or symptoms they are feeling as part of their menstrual cycle (such as headaches, cramps, breast tenderness, or emotional side-effects).
Also, it is beneficial to include anything that might have affected your BBT. No one is perfect. We all have busy schedules, and sometimes things come up. It is important to note things like sleeping late, having disrupted sleep, drinking alcohol, or being sick.
Because the purpose of the BBT chart is to help you effectively time intercourse, you will want to include when you had intercourse during your cycle. You can indicate this just by circling the date or by using symbols like a star, a smiley face, or even a heart on the dates you had intercourse.
Again, because you are looking for trends to maximize your chances for success, some women include even more details about their love-making, such as positions used or whether or not they achieved an orgasm. How much information you record is entirely up to you.