Now that pregnancy tests you buy over the counter are so sensitive, they can detect the presence of a pregnancy before the missed period—sometimes as early as 6 days before a missed period. Unless you buy a digital test, you will have a pregnancy test that involves two lines. One line is considered the control line and is a way of knowing whether or not the test worked at all.
If you see 2 lines, it generally means you are pregnant. So what if you see an extremely faint line on the pregnancy test? It can mean that you are very early in the pregnancy—so early that a faint blue line is all that will show up for a few days. It can also mean you are not having healthy enough levels of HCG in the urine and that the pregnancy is not healthy. You may have to see the doctor in order to tell the difference. Blood tests for pregnancy can help determine the health of a pregnancy.