The ovulation test measures the concentration of the ovulation-inducing hormone LH (luteinizing hormone).
24-36 hours before ovulation, the level of LH hormone increases significantly. If you use an ovulation test, it will turn positive when the hormone rises indicating that you are ovulating.
You can recognize a positive ovulation test when the test line is as dark or even darker than the control line.
It is recommended to start testing for ovulation 2-3 days before the expected ovulation. Ovulation typically occurs 14 days before your menstruation starts. So, if your cycle is 28 days, you should start testing for ovulation on day 11 or 12 (day 1 being the first day of your last menstruation).
If the length of your cycle is still unknown, it is recommended to start testing on day 10 or 11 of the cycle.
Pregnancy tests are designed to react to the pregnancy hormone Human Chorionic Gonadotropin, also known as hCG. This hormone increases if a fertilized egg implants in the woman's uterus. Therefore, an elevated level of hCG in a woman's urine indicates that she is pregnant.
Pregnancy tests have two antibody lines. The first one is the control line, which becomes colored when dipped in urine. If the control line appears with color, it confirms that the test is working properly. The second line is called the test line, and this line only becomes colored if your urine contains the amount of hCG that the pregnancy test is sensitive to.
hCG begins to rise when the fertilized egg has implanted itself 5-10 days after fertilization by a sperm cell and has started to divide. The level of the pregnancy hormone hCG then increases rapidly, doubling every three days in the first 12 weeks of pregnancy.
Clinical tests have shown that 99% of all pregnant women can test positive on a standard pregnancy test on the day of their expected menstruation.
The reliability of early and standard pregnancy tests today is so high that false positive results are extremely rare. If your test is positive - meaning a colored line appears on the test line of the pregnancy test within the specified time frame - then you are pregnant.
However, some women may still experience menstruation on their expected period date or a few days later, leading them to think that the pregnancy test was a false positive. In most cases, this is due to a biochemical miscarriage, which occurs around weeks 3-5 of pregnancy. This is a type of miscarriage that occurs during a period when pregnancy can only be detected through a pregnancy test or blood test, and an ultrasound scan would not show a developing embryo with a heartbeat. Nonetheless, if a colored line appears within the designated time frame stated in the instructions, it indicates an elevated hCG level, meaning that you are - or were - pregnant.
Please note that certain medications, such as Ovitrelle, can cause hCG levels to rise without being pregnant.