What can affect home pregnancy test results?

Testing too soon: Main thing is timing-it takes time (up to 2 wks) for your urinary levels of HCG to get elevated enough to be detected. Over-the-counter tests aren't always as sensitive as tests at your doctor's office, but even those usually take at least a few days after you're late to turn positive. Recheck 1-2 weeks later if you're late for your period & suspect you might be pregnant.