Taking your basal body temperature (BBT) is very easy and only takes a few minutes. (Is basal body temperature a reliable source to confirm the occurrence of ovulation?) It's important, however, to follow some general rules:

  • Measure your basal body temperature every morning after at least three hours of uninterrupted sleep.
  • Take your temperature before rising or doing anything else, like taking a sip of water, making a phone call, or going to the bathroom. Keep the thermometer by your bed, so that you don't have to look for it in the morning.
  • Measure your BBT at the same time, or within a half-hour of this time, every day. Note down the time of the measurement.
  • If you're using a digital thermometer, wait for the signal or beep (usually about one minute). If you're using a glass thermometer, wait about five minutes. Remember to shake it before going to bed, so you don't make sudden movements in the morning before taking your temperature.
  • Take your BBT orally or vaginally. Decide on one or the other, because your temperature varies between the two.
  • Try to note down or enter your BBT as soon as possible after taking your temperature (if you don't have a computer nearby, keep a notepad and pen by your bed.)