some can be used up to 5 days before period is due, but they are not very accurate.
Really you need to wait until your period is late to stand any chance of an accurate result, and even then its often best to wait until a week overdue.
the ones that purport t be able to tell early have a little star on them saying something like *accurate in 28% of cases, or something to that effect. Waste of money if you ask me, as red has said, wait till your period is overdue at least
I did 5 tests and all were negative when in fact, I was pregnant, and I took all tests at least a week after my due date. My advice is don't waste your money, take a sample to your doctor and get them to do it for free, but wait a week until after your period is due. I hope the result is the one you want. x