There are three letters on your test cassette – C, G and M. A line should appear next to the C, regardless of your result (this is the control line and confirms your test is working). If this is the only line you see, you are negative to both antibodies and do not appear to have, or have had, COVID-19. nnA line next to the G means you have previously had the infection and now have antibodies. A line next to the M means you may be currently infected and may be infectious to others. In this case, you should take all precautions, self-isolate and monitor your symptoms. You should book a test on the NHS to confirm whether you do indeed have COVID-19.