Hi Anonymous, The test line can appear as faint when users who are positive test inside of the window period, this may be as the test can detect slight infection but the level of antibodies in the blood is low and therefore binding to the test strip will be minimal. The results are designed to be read in natural light, you do not need to shine direct light onto the test strip is order to read your result so I would not worry that you have missed seeing a faint test line. As long as you received the control line then your test has worked perfectly and your result is negative. I hope this helps, Becky