False Positive Pregnancy Tests

If you are trying to get pregnant, the desire to take a pregnancy test can be powerful.        Instead of waiting for their period to be late, most women will decide to test as early as possible.     Testing before your period is due is a major cause of what  some women call false positive pregnancy test results.   When someone says they had a false positive result, it usually means that additional pregnancy tests were not positive like the original test.

While many  blame the quality of the pregnancy test for giving the wrong result, a truly “false positive” test result, due to a faulty home pregnancy test, is very rare.  Many of the causes of a false positive result can linked to early pregnancy loss or not reading or using the pregnancy test correctly.


Why did I get a positive pregnancy test and a negative one?


What Can Cause False Positive Pregnancy Test Results?


The following reasons explain several situations where positive and then negative test results can happen.


Medically Related Causes


  • You’ve had a chemical pregnancy.  The unfortunate fact is about 25% of all pregnancies end up being a chemical pregnancy.     This happens when a fertilized egg stops developing, after implantation,  because of an abnormality or some other reason. The fertilized egg never becomes an embryo, but you may have enough hCG to test positive.  Due to the super sensitive pregnancy tests available,  women can detect pregnancy in the very, very early stages.    The joy of discovering your pregnancy early also has the chance of crushing heartbreak if an early miscarriage happens.  You can avoid the rollercoaster of emotions from a chemical pregnancy if you wait longer to test.


  • 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 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.


  • You are taking a fertility drug that contains hCG.   If you had a hCG trigger shot, you need to make sure the shot has cleared your system.   Fertility doctors suggest waiting about 14 days  after a hCG shot before taking a pregnancy test. Testing before this time may very well likely produce a positive result when you are not truly pregnant.


Pregnancy Test Related Causes


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


  • You’re using an expired pregnancy test.  An expired  pregnancy test usually may not able to register the hCG.  It could give you no results at all or a possibly false negative result.   Tests that have been exposed to heat or moisture can also result in a false positive pregnancy test result.


  • 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 read the test after the time stated in the instructions, the results need to be considered invalid.    Reading after the correct time frame can show results that you could misinterpret as a positive result.


There are rare cases when you can get positive pregnancy test results when you are not pregnant.

  • Some medical conditions, like cancer, can cause your body to produce hCG even when you’re not pregnant.


  • Some medications can also cause false positive results.     WebMD reports  “… certain drugs, such as tranquilizers, anti-convulsants, or hypnotics, may also cause false-positive results.”.


Use your common sense if you are experiencing what you think are early pregnancy signs.  Contact your doctor to discuss your symptoms and possibly get a  blood pregnancy test.