No prescription is required. New technology has made the tests highly reliable and easy to use. Results take only five minutes to obtain, and the test can be given as early as the first day of a missed period. The tests detect a hormone in the urine called human chorionic gonadotropin, which is produced by the placenta. Since the hormone is most easily detected in the morning, some kits require that the test be done in the early morning.
Most tests have the user urinate on a plastic indicator stick about the size of a nail file.
If the hormone is detected, a chemical reaction registers on a gauge built into the indicator stick. If the woman is pregnant, a colored circle, bar, or plus sign appears on the gauge on the indicator stick. If the results are negative, the window remains unchanged. When test results are positive, the test is 99 percent accurate. They are 80 percent accurate if the results are negative.