Luteinizing hormone (or LH) in elevated quantities causes ovulation (the release of the egg - or ovum - from the ovarian follicle). During the menstrual cycle only a small amount of LH is made, but in the middle of the cycle LH briefly and dramatically increases. This increase is called the "LH surge" and precedes ovulation. Conception is most likely to occur within thirty-six hours following the LH surge. The LH Ovulation Test is specifically designed to detect your LH surge - the time when you are likely to ovulate. If you receive a positive on an lh test, you are in your most fertile phase of your menstrual cycle.
