Your body produces LH (Luteinizing Hormone) every day during your cycle and you will always have some amount present in the urine.
That is why you will see a test line on most of your tests. This is a healthy sign. Just remember, that the result is considered positive if the test line is at the same intensity or darker than the control line.
In order to be sure if the test strip is showing a true positive result, it is important to continue testing after you receive the same intensity lines. The test line may become even darker than the control line or it may become pale again, indicating that the previous test result was a true surge. The positive test color line may vary depending on the individual. While some ladies can see the test line match the control line prior to their ovulation peak others see test lines a way darker than the control one. When test line becomes lighter than control, that would indicate that your LH surge is over and ovulation will take place within the next 24 to 48 hours.
For some women LH surge can last a couple of days, while for others it only lasts about 12 hours. Please keep in mind that every cycle is unique. Some women do not ovulate every cycle and will not see an increase in LH levels during these non-ovulatory cycles.
Example: Bottom tests show negative result. Middle test shows that you may be approaching LH surge and the top tests show a positive test result.