Does the line test line have to be darker than the control line to be considered positive?
As a general rule, YES. The test line should be as dark as or darker than the control line. In some cases and with some brands, it’s possible to never see a true positive though. Particularly with some of the cheaper online test strips, using the OPK in conjunction with other ovulation detection methods (temperature charting, cervical mucus, etc) can be useful for a couple of cycles to figure out what will look like a positive to you.
