Will a pregnancy test be accurate 15 days after sex?

More reliable later: A urine pregnancy test, done correctly, gives a reliable result by 3 weeks after sex (3 weeks after when conception might have occurred) or 1 week after missing a period. If done sooner, a positive result is likely real but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.