Fertility Testing for Women
Ovulation Testing > Basal Body Temperature Testing
Basal Body Temperature (BBT) Testing measures subtle changes in a woman’s body temperature which occur due to ovulation. After ovulation, the ovary produces progesterone, which causes a woman’s temperature to increase by about ½ of a degree on the Fahrenheit scale. When a special BBT thermometer is used on a daily basis, one can determine both if a woman ovulates and how long her luteal phase lasts. Proper technique is essential in order for your physician to interpret the results.
Basal Body Temperature Charting Technique:
- Obtain a BBT thermometer, available at your drug store.
- Place the thermometer at your bedside.
- The day after your menses begin, start recording your temperature.
- Each morning, upon waking and before rising or any morning activity and before drinking anything, take your temperature.
- Record the temperature on a BBT graph.
- Keep recording on a daily basis until your next menses begins.
- The temperature should remain elevated for at least 11 days.
- If you do not get a temperature rise, or if the rise does not last 11 days, consult your doctor.
As seen below, a normal temperature rise will last for a minimum of 11 days. It can take up to three days after ovulation for the temperature to rise; however, in our experience most women experience temperature rises on the same day or a day later than when an ovulation predictor kit turns positive.
It is important to know: intercourse in the 2-3 days before the temperature rises is most likely to result in pregnancy.
Below are some examples of normal and abnormal BBT graphs.
An abnormal BBT should be investigated. If you have questions about your BBT, let us help you evaluate and understand the information.
This BBT chart shows ovulation with an adequate duration of the luteal phase. Notice that the temperature stayed elevated for 11 days or more.
This BBT chart shows ovulation with a short luteal phase. The temperature did not stay elevated for 11 days. A short luteal phase can be a cause of infertility and/or recurrent pregnancy loss, and should be investigated.
This BBT chart shows no evidence of ovulation in this cycle. The one-day spike at day 23 is likely just a random event. A BBT chart like this does not mean that a woman is never ovulating, only that it did not occur in this cycle. However, irregular ovulation should be investigated.
See Ovulation Predictor Kits for more Ovulation Testing information