How to Detect an LH Surge

LH refers to luteinizing hormone, the hormone necessary for ovulation to occur. Each month, about two weeks after menstruation, there is a sudden and sharp increase in LH, causing the ovary to release the egg (ovulation). There are tests to detect this surge that allow a woman to know when ovulation is about to occur. Predicting ovulation is important for women trying to conceive as the opportunity for fertilization lasts only a few days and happens once a month.

Instructions

• 1

  Evaluate your menstrual cycle. In order to know the best time to use the LH test, it is important to understand your menstrual cycle. To determine the length of your cycle, count the number of days from the first day of bleeding until the day before your next period starts. According to the American Congress of Obstetricians and Gynecologists, most cycles are about 28 to 32 days long, but cycle length varies from woman to woman and from month to month. Take cycle measurements for at least three months in order to get an accurate estimate.

• 2

  Determine when to test. Since the LH surge is very short, it is important to test at precisely the right time of the month and the right time of the day. To determine the best day to test, use the following formula. For a 28 day cycle, test on day 12 (from first day of menstrual bleeding). If your cycle is more than 28 days, add a day to each number. For example, 29 day cycles test on day 13, 30 day cycles test on day 14. If your cycle is less than 28 days, subtract a day. So 27 day cycles test on day 11. LH is normally produced in the morning, so tests are most accurate around the middle of the afternoon.

• 3

  Purchase a home ovulation detection kit. Most ovulation detection tests test urine using a container or require testing midstream. For container tests, you dip a test strip into the urine-filled container and hold it there for a few seconds. For midstream tests, the test strip is used during urination.

• 4

  Read the results of the ovulation test. Most tests require a short wait of up to 5 minutes before reading. All tests will have a comparison or "control" line that verifies the test is working. The test line shows whether ovulation has occurred. Usually, a positive test will show a test line that is darker than the comparison line and a negative test will show a color that is much lighter or hardly visible. It is important to consider that there is always a small amount of LH in the body, so a light color test line does not necessarily mean ovulation is occurring.

• 5

  Determine the best fertilization window. According to the American Congress of Obstetricians and Gynecologists, an egg typically lives between 12 and 24 hours after ovulation. If your LH test is positive and ovulation is beginning, then the optimal fertilization time is between between one and three days after the LH surge (giving an extra window of time to account for variation).