Because the most common form of emergency contraception is known colloquially as the morning-after pill, some people may assume that it's only effective in the 24 hours after unprotected sex. Fortunately, Dr. Polyakov explained that, depending on the formula, the pill can be taken up to three to five days afterward and still be effective. However, the morning-after pill becomes less effective the longer you wait. It's also important to note that the pill is not 100 percent effective, even when taken quickly and correctly.