(HealthDay News) -- Home pregnancy tests are designed to detect a certain hormone that's present in a woman's blood and urine when she's pregnant.

The test must be administered carefully, following all of the product's written instructions.

The Womenshealth.gov web site offers these general guidelines for home pregnancy tests:

  • Make sure the product is not past its expiration date.
  • Follow the label instructions carefully.
  • Wait 10 minutes before checking the results.
  • Take the test first thing in the morning.
  • Wait at least a week after missing your period before taking the test.