Home pregnancy tests: Can you trust the results?

Could you be pregnant? Get answers to common questions about home pregnancy tests.

By Mayo Clinic Staff

Taking a home pregnancy test can be nerve-wracking, especially if you're not sure whether you can trust the results. Know when and how to take a home pregnancy test — as well as some of the possible pitfalls of home testing.

When should I take a home pregnancy test?

Many home pregnancy tests claim to be accurate as early as the first day of a missed period — or even before. You're likely to get more accurate results, however, if you wait until after the first day of your missed period or, better yet, one week after your missed period.

Why wait? Shortly after a fertilized egg attaches to your uterine lining (implantation), the placenta forms and produces the hormone human chorionic gonadotropin (HCG). This hormone enters your bloodstream and urine. During early pregnancy, the HCG concentration increases rapidly — doubling every two to three days. The earlier you take the home pregnancy test, the harder it might be for the test to detect HCG. Keep in mind that the exact timing of ovulation might vary among women or even from month to month, and the fertilized egg can implant in the uterus at different times. This can affect when HCG production begins and becomes detectable.

If it's important to confirm your pregnancy right away, depending on how far along you are in your pregnancy, your health care provider might recommend that you have an ultrasound, repeat a urine test in the hospital or clinic lab, or have a blood test to measure your HCG.

Are there different types of home pregnancy tests?

With most tests, you place the end of a dipstick in your urine stream or immerse the dipstick in a container of collected urine. A few minutes later, the dipstick reveals the test result — often as a plus or minus sign, one line or two lines, or the words "pregnant" or "not pregnant" on a strip or screen.

However, some home pregnancy tests are more sensitive than others. In other words, in some tests the amount of HCG needed to be detected in the urine to produce a positive test result is lower.

Always check the test's expiration date and read the instructions carefully before you take the test.

How accurate are home pregnancy tests?

Many home pregnancy tests claim to be 99 percent accurate. However, research suggests that many home pregnancy tests are not sensitive enough to diagnose pregnancy in women who have recently missed a period. For the most reliable results, wait to take the test until one week after your missed period.

Dec. 02, 2015 See more In-depth