While a blood test is the most reliable way to find out if you're pregnant, home pregnancy tests can also be very accurate -- if you use them correctly. Follow the instructions to the letter and don't use an expired test.
You may also want to take some of the tests' claims on how quickly they work with a grain of salt. Home pregnancy tests can't always detect low levels of hCG, so if you take a test right away, you may not get an accurate result. Waiting at least until you miss your period allows levels of the hormone to build up enough for the test to detect them, and some women may need to wait until a week after a missed period for best results.
Keep in mind that your body doesn't start producing hCG until the fertilized egg implants itself in the uterine lining. Exact ovulation and implantation dates vary by woman. It's quite possible that you could miss a period and be pregnant, but not yet be producing hCG. In that case, a pregnancy test won't work.
Pregnancy tests may also produce false positives and negatives. False positives are extremely rare, but they can happen in the following situations:
- You were recently pregnant.
- You take medicine containing hCG.
- You have blood or protein in your urine.
- You have ovarian cysts or an ectopic pregnancy.
- You're going through menopause
False negatives can be more common, and many false negatives are due to these user errors:
- The test is past its expiration date.
- You're taking the test too soon.
- You didn't follow the instructions. The test needs time to work, but if you give it too much time, you may get the wrong results.
- Your urine is diluted. Take your test when you get up and your urine is its most concentrated.
If you test yourself and get results you don't think are right, wait a few days and take another test. If the results are mixed or you don't get your period, see your doctor, who can do a blood test or discover other factors that may be contributing to a missed period. Irregular periods may also be partly to blame for erroneous test results.
Read on for more information about pregnancy tests.
- American Pregnancy Association. "Taking a Pregnancy Test." March 2011 (April 18, 2011)http://www.americanpregnancy.org/gettingpregnant/takingapregnancytest.html
- American Pregnancy Association. "Understanding Pregnancy Tests: Urine & Blood." March 2011. (April 18, 2011)http://www.americanpregnancy.org/gettingpregnant/understandpregnancytests.html
- Healthwise, WebMD. "Multiple Pregnancy: Twins or More - Exams and Tests." July 16, 2009. (April 18, 2011)http://www.webmd.com/baby/tc/multiple-pregnancy-twins-or-more-exams-and-tests
- Mayo Clinic. "Home Pregnancy Tests: Can you trust the results?" Oct. 30, 2010 (April 18, 2011)http://www.mayoclinic.com/health/home-pregnancy-tests/PR00100
- National Women's Health Information Center. "Pregnancy Tests." April 1, 2006. (April 18, 2011)http://www.womenshealth.gov/faq/pregnancy-tests.cfm
- WebMD. "Pregnancy Tests." Feb. 17, 2010. (April 18, 2011)http://www.webmd.com/baby/guide/pregnancy-tests