There are hormones (LH and oestrogen) which rise one to two days before ovulation takes place for a woman. These hormones are the ones responsible for the egg to be released from the ovary. Hence, the ovulation test strip is different from measuring your basal body temperature in that it lets you know BEFORE you’re going to ovulate. However, having a regular period is helpful to be able to detect ovulation in this manner. Women with PCOS who have irregular periods will have issues with timing the test, and those with an elevated LH hormone level will have a positive ovulation test all the time.