Try reading the insert that comes with the test. The results get messed up after a certain amount of time. No matter what prego-test you take, you should follow up a few days to a week later. And take it in the morning, before you use the restroom for the first time. The hormones are more concentrated then, and you're more likely to get an accurate result if you are pregnant.
NEVER trust a pregnancy test that has been sitting out for an hour! Take the test, wait the allotted amount of time prior to looking at the results, and then that's it. I used dollar store tests, and they were accurate. heck, they all IMMEDIATELY has positive results. Took them in the morning: two tests were 2 days and 5 days before missed period, and three were day of missed period and 3 and 7 days later.
at 10:30 PM on May. 14, 2009