It is important to start using the ovulation prediction kit at the right time during the menstrual cycle. This will require a keeping a journal of all the menstrual cycles for a few months to a year before conception is planned. Or you can use the BabyMed OPK Calculator. Not every woman has a normal 28 day menstrual cycle. As a matter of fact, most women do not have a 28 day cycle every time. After noting the time between menstrual periods for a few months, the woman can add together all of the days and divide by the number months the menstrual cycles were recorded. This will give the woman the average number of days between her menstrual cycle.
Once the average cycle has been noted, the woman can start taking the ovulation tests with the median day in the middle of the tests. For instance, if a woman's menstrual cycle average 32 days and her median is day 16, she could start testing for ovulation on day 13 and continue through day 19. Most ovulation prediction kits will include enough tests to cover several days before the median day and several days after.
Not all woman are created equal in terms of ovulation. In some cases, if conception is difficult, testing throughout the month may reveal that ovulation is occurring very early or very late in the menstrual cycle. Each woman is different and the ovulation prediction test will only work effectively if used near the date of egg release.