If you see only one 'T' line or don't see any lines at all, it means that the result of your test is invalid (see the picture below) and you need to re-take the test.
However, when you see two lines (no matter how faint or dark the 'T' line is), it means that the result of your test is negative (see the picture below). If the “T” line is very faint, that means that the concentration of THC in your body is somewhere around 50 ng/ml, which is the cut-off level of the test strips.