Period refers to menstruation. Ovulation test strips are used to predict ovulation by detecting the peak level of luteinizing hormone, and luteinizing hormone levels are at their lowest during menstruation, so ovulation test strips usually don’t turn red when menstruation is approaching. Ovulation test strips are mainly used to monitor ovulation by detecting the level of luteinizing hormone, which is generally highest at the time of ovulation and then gradually decreases, reaching its lowest level at the time of menstruation. If the color of ovulation test paper turns red, it means that ovulation will occur in the last 1-2 days, that is, the level of luteinizing hormone increases, and the level of luteinizing hormone is the lowest in the menstrual period, so the ovulation test paper will not change to red in the near future of menstruation. Generally, ovulation occurs about 14 days before the next menstrual period, and it is recommended to have intercourse during the ovulation period to increase the chances of conception.