False Positive Pregnancy Tests

Home Pregnancy Tests

The best way to get accurate results when using a home pregnancy test is to wait until your period late. At that time, the level of hCG in your system will be large enough that all of the pregnancy tests on the market will be able to detect it, producing a positive pregnancy test result.

Most women, who are trying to get pregnant, prefer to find out as soon as possible. That “two week wait” becomes unbearable. There are many home pregnancy tests on the market that claim you can test much earlier, usually 4 or 5 days before your period is due. These early test pregnancy tests are typically about 97% accurate, when all the instructions are follow exactly and you read the results within the time frame listed in the instructions.

What Can Cause False Positive Pregnancy Test Results?

A truly “false positive” test result, due to a faulty home pregnancy test is fairly rare. A positive result which is not repeatable, with subsequent home pregnancy tests, is usually because of one of these reasons:

  • You mistake an evaporation line for a positive result. Sometimes pregnancy tests will leave a faint colorless line in the testing area as the test area starts to dry. If there is no distinct color to the line, you can not interpret it as a positive result.


  • You’ve had a miscarriage or a pregnancy ended in the previous eight weeks. It can take that long for the hCG levels in your system to drop.


  • You are taking a fertility drug that contains hCG. These aren’t particularly common, but they are occasionally used. If you are undergoing fertility treatments and have had a hCG (Human Chorionic Gonadotropin) trigger shot, you will need to make sure the shot has had enough time to metabolize through and clear your system. Fertility doctors suggest waiting about 14 days for your system to be clear of the hCG before taking a pregnancy test. Testing before this time may very well likely produce a positive result when you are not truly pregnant.


  • You may missed the reaction time frame. You really need to follow the instructions included with your home pregnancy test exactly. The manufacturer lets you know how long you should allow the test to sit before interpreting the results. If you let the test sit for longer than the instructions state, any results you interpret need to be considered invalid. Reading after the recommended time frame has passed can show results that you will misinterpret as a positive result.


  • You’re using an expired pregnancy test. Usually, a pregnancy test that’s passed its expiration will just not be able to register the hCG, and you’d have a false negative. However, depending on whether or not the test has been exposed to heat or moisture, there is a chance you might get a false positive pregnancy test.


  • You have certain medical conditions. There are some medical conditions that can cause your body to produce hCG even when you’re not pregnant.


  • You’ve had a chemical pregnancy. As unfortunate as it is, about 25% of all pregnancies end up being a chemical pregnancy, also known as an early miscarriage. This happens when a fertilized egg implants in your uterus and your body produces hCG, but then the fertilized egg stops developing because of an abnormality or some other reason. The fertilized egg never becomes an embryo, but you may have enough hCG to test positive. With the advancement in sensitivity of the home pregnancy tests on the market today, women are able to detect pregnancy in the very, very early stages. This is the downside of the super sensitive pregnancy tests – the joy of discovering pregnancy very early on, followed by crushing heartbreak if an early miscarriage occurs.


  • You have an ectopic pregnancy. This means that the fertilized egg implants somewhere other than the uterus. There is no way to move the fertilized egg into the uterus, and it will not correctly develop. An ectopic pregnancy can result in a false positive pregnancy test, although it does not always do so.


If you feel you are having early pregnancy symptoms and not getting the results you think you should be from your home pregnancy tests, you should contact your doctor for a blood pregnancy test.