Hello and welcome to Healthcare Magic. Thanks for your query.
I'm not sure whether you are referring to 18 days after a missed period or 18 days after unprotected sexual intercourse. 18 days after a missed period is enough time for a urine pregnancy
test to detect pregnancy, and the likelihood of false negatives is very minimal.
is a hormonal
tablet which is given to induce bleeding, when there is a delayed menstrual period . Usually bleeding occurs 3 to 4 days after the tablet is stopped, i.e. it is actually called "withdrawal bleeding". In some cases, it may take a little longer time for the bleeding to start. So, I would advise you to wait for a few more days.
Dr. Sheeba Stephen