How to take and record your basal body temperature

How to take and record your basal body temperature (BBT)

It is important to use an accurate digital BBT thermometer. Choose a digital BBT thermometer that gives a quick reading, beeps when it is finished recording the temperature and is easy to read. This can make a difference when you are bleary-eyed first thing in the morning.

Ideally your thermometer will also store your reading for you, though it is recommended you record your temperature in your chart straight away.

It is best if you can establish a routine where you enter your data at the same time every day just to form the habit so you will not forget. This is because missing data, especially temperature data can skew the interpretation of your chart. Once a routine is established, taking and recording your temperature will probably start to feel as habitual as brushing your teeth.


Your temperature data will be most reliable if you follow these guidelines. Not following these guidelines may make your chart difficult to read and may make detecting ovulation more difficult.

  • Take your temperature before getting up in the morning as any activity can raise your BBT.
  • Take your temperature at the same time every morning.
  • Take your temperature after at least three consecutive hours of sleep.
  • Keep your thermometer accessible and near your bed so you do not have to get up to get it.
  • Use the same thermometer throughout your cycle if possible. If it breaks or the battery runs out and you use a new one, make a note of it on your chart.
  •  Record your temperature straight after you take it.
  • If you must use a heating pad or electric blanket, keep it at the same setting throughout your cycle. Make a note of its use.
  • Take your temperature before doing anything else including eating, drinking or going to the bathroom. If circumstances arise that prevent you from taking your temperature right away, take it as soon as you are able and make a note of the circumstances.
  • If you have special circumstances on a temporary or an ongoing basis and you are unable to follow all the above guidelines, keep taking your temperature anyway following the guidelines as closely as possible. Make a note of your special circumstances.
  • Enter your temperature and always record the time you took it on your data entry page. The time you took your temperature is also important for the analysis. 

Factors that influence your BBT

There are certain factors that can influence your basal body temperature. These should be noted on your chart. 

  • Fever, illness and infections (even those that do not produce a fever), cold and a sore throat
  • Drugs and medications
  • Alcohol (especially in large quantities, though all alcohol consumption should be recorded) and smoking
  • Emotional stress, physical stress and excitement
  • Sleep disturbances (insomnia, night-waking, upsetting dreams, poor sleep) and change in waking time
  • Jet lag and travel
  • Change of climate
  • Use of electric blanket and change of room temperature