IMPORTANT: If a woman has a fever or other changes in body temperature, the BBT method will be difficult to use.

Take body temperature daily
  • The woman takes her body temperature at the same time each morning before she gets out of bed and before she eats anything. She records her temperature on a special graph.
  • She watches for her temperature to rise slightly—0.2° to 0.5°C (0.4° to 1.0°F)— just after ovulation (usually about midway through the menstrual cycle).
Avoid sex or use another method until 3 days after the temperature rise
  • The couple avoids vaginal sex, or uses condoms or a diaphragm from the first day of monthly bleeding until 3 days after the woman’s temperature has risen above her regular temperature. They can also use withdrawal or spermicides, but these are less effective.
Resume unprotected sex until next monthly bleeding begins
  • When the woman’s temperature has risen above her regular temperature and stayed higher for 3 full days, ovulation has occurred and the fertile period has passed.
  • The couple can have unprotected sex on the 4th day and until her next monthly bleeding begins.
Basal Graph