Ovulation tests work by detecting a search surge of the luteinizing hormone also known as LH. During your menstrual cycle your body only produces a small amount of LH. Then, approximately halfway through your cycle, the LH surges to aid in the release of the ovum from the ovary. The LH surge occurs approximately 12 to 48 hours before ovulation, however, 36 hours is the accepted average time between the surge and ovulation.
Unlike pregnancy tests, the best time to test for the LH surge is in the afternoon. LH is produced by your body during the morning and will not appear in your urine until the afternoon. Also, consistency is key in accurately predicting ovulation. Make sure to test at the same time each day to maximize the accuracy of the test.
The test strip, once activated, will show one or two lines. The C line is the control line, the T line is the test line. The C line always appears, it's the line that shows that the test is working. The T line denotes positive detection of the LH hormone - which means you are ovulating.Please note though, if the T line is very faint the test is negative. Only a line that is as dark as, or darker, than the C line denotes a positive test.