I took a pregnancy test last night it came up negative, but for some reason I decided to look again this morning ad it was positive. What does that mean? Is it because my urine sat too long, or did it just take longer to show?

First morning pee is the best pee to test for pregnancy... so I have heard.

It means nothing if it was outside the allowable time frame for reading.

This morning your result was positive due to evaporation, not pregnancy. Any result you see after the window of time specified on the directions is not accurate. The test is most reliable if taken using first morning urine. Please retake the test in the morning and follow the directions EXACTLY.

It means you did not read the instructions that tell you, it must be read within so many minutes. It means you needed to have thrown it in the trash, not leaving it laying around.

It means nothing. Outside the time, they all would turn positive after enough hours

There are instructions that must be followed to make the test accurate. It will tell you, in the instructions, that any change in result after a certain amount of time, is not an accurate result.

Use first morning urine, follow the directions exactly.

How late is your period?