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How To Take Your Basal Body Temperature

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Updated November 10, 2010

Basal Body Temperature Chart with Ovulation / iStockPhoto

Basal Body Temperature Chart with Ovulation

Photo © iStockPhoto

Charting your basal body temperature (BBT) is a relatively easy and inexpensive way to track ovulation. Your basal body temperature is your body’s temperature at rest. After ovulation, your basal body temperature will shift up by at least four-tenths of a degree. If your temperature remains elevated for at least three days, you can be pretty sure that ovulation has occurred on the day before the temperature rise.

Because the shift in temperature is so small, it’s important to take your temperature at the exact same time every morning, before you get up or move.

Difficulty: Easy
Time Required: A few minutes every morning

Here's How:

  1. Before you go to bed at night, place a thermometer within your reach by your bed. It’s very important that you can reach this thermometer without needing to get up or move around when you wake up. Getting out of bed, or even sitting up, will throw off your temperature and skew the results.
  2. You should take your temperature at the same time every morning, with no more than a 30 minute difference from morning to morning.
  3. When you wake up, reach for your thermometer and take your temperature. Do not get up to go to the bathroom, and don’t get up to turn off your alarm (keep that near by, too, if you can’t stand it going off while taking your temperature.)
  4. You can take your temperature orally or vaginally. It doesn’t matter which way you choose, as long as choose one and stick with it day to day. If you tend to sleep with your mouth open, taking your temperature vaginally may be better.
  5. Follow the directions for your thermometer to get the best reading. If you’re using a mercury thermometer, make sure you leave it in place long enough to get a final reading. That may take up to four or five minutes.

    (If you do use a mercury thermometer, be sure to shake it down before you go to bed at night. Shaking it down when you wake up can throw off your results.)
  6. After you take your temperature, write it down. Some BBT thermometers come with a memory function, which is nice, though you can use a regular thermometer. Keep a pen and paper by your bed so you can jot down your temperature and the time you woke up, until you have time to fill this information into your chart.

Tips:

  1. If you need to wake up extra early, or later than usual, take your temperature as you always do (without getting out of bed, right when you wake up). Mark the difference in time on your chart.
  2. You need to have slept at least four straight hours for your temperature to be accurate. If you get up often at night to go to the bathroom, or have trouble sleeping, this can throw off your results. You should take your temperature anyway, and note that your sleep was interrupted on your chart.
  3. Basal body temperature charting does not work for everyone. If you don’t notice a sustained rise in temperature, it doesn’t necessarily mean that you are not ovulating. Still, you should speak to your doctor.
  4. While basal body temperature charting can pinpoint when ovulation occurred, it isn’t a good way to predict ovulation. Since you need to have sexual intercourse before ovulation if you want to get pregnant, you should look for other signs of ovulation so you can time sexual intercourse better. One way to predict ovulation is by tracking your cervical mucus.
  5. Learn how to chart your basal body temperature in this article.

What You Need

  • thermometer
  • pen and paper
  • ovulation chart
  • clock

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