The One Step Urine Ovulation LH Test will help you find the time when you are most able to become pregnant. It can help you plan your pregnancy. How this home test works: The One Step ovulation test will help you find the time when you are most able to become pregnant. It can help you plan your pregnancy. Luteinizing hormone(LH) is always present in human urine. It increases just before a woman most fertile day of the month. This LH increase triggers ovulation. During ovulation an egg is released from the ovary. Because the egg can be fertilized only 12 to 36 hours after ovulation, detecting ovulation in advance is very important. You may do this test at any time of the day, but you should test at approximately the same time each day. Reduce your liquid intake for 2 hours before testing. To decide when to begin testing, determine the length of your normal menstrual cycle. The length of your cycle is from the beginning of one period to the beginning of the next (count the first day of bleeding or spotting as day 1). If your cycle length is irregular, that is, if it varies by more than a few days each month, take the average number of days for the last 3 months. Use the chart to work out the day you should begin testing. The day you begin testing is listed opposite the number of days in your normal cycle. This product is recommended for a professional use