Could medications interfere with test results?

Fertility drugs or other medications that contain HCG might interfere with home pregnancy test results. However, most medications, including antibiotics and birth control pills, don't affect the accuracy of home pregnancy tests.

Could a positive result be wrong?

Although rare, it's possible to get a positive result from a home pregnancy test when you're not actually pregnant. This is known as a false-positive.

A false-positive might happen if you had a pregnancy loss soon after the fertilized egg attached to your uterine lining (biochemical pregnancy) or you take a pregnancy test too soon after taking a fertility drug that contains HCG. An ectopic pregnancy or menopause also might contribute to misleading test results.

Could a negative result be wrong?

It's possible to get a negative result from a home pregnancy test when you're actually pregnant. This is known as a false-negative — and it's much more likely to occur than is a false-positive. You might get a false-negative if you:

  • Take the test too early. The earlier after a missed period that you take a home pregnancy test, the harder it is for the test to detect HCG. For the most accurate results, take the test one week after a missed period — when the level of HCG in your urine is most likely to be detectable. If you can't wait that long, ask your health care provider for a blood test.
  • Check test results too soon. Be sure to give the test time to work. Consider setting a timer according to the package instructions.
  • Use diluted urine. Drinking too much fluid before taking a home pregnancy test might cause a false-negative result. For the most accurate results, take the test first thing in the morning — when your urine is the most concentrated.

What happens next?

Based on your test results, consider taking the following steps:

  • Your home pregnancy test is positive, or you've taken a few home pregnancy tests and gotten mixed results. Make an appointment with your health care provider. You might need a blood test or pelvic exam to confirm your pregnancy. The sooner your pregnancy is confirmed, the sooner you can begin prenatal care.
  • Your home pregnancy test is negative. If your period doesn't begin, repeat the test in a few days or one week — especially if you took the test before or shortly after a missed period.
  • You continue to get negative test results, but your period doesn't begin or you still think you might be pregnant. Check with your health care provider. Many factors can lead to missed periods, including illness, strenuous exercise, weight loss, stress and hormonal imbalances. If you're not pregnant, your health care provider can help you get your menstrual cycle back on track.
Jan. 05, 2013 See more In-depth