What Causes a False Positive or Negative Pregnancy Test?

Are you wondering if your pregnancy test results are right? Home pregnancy tests are convenient and easy to take, but there are many variances that could give you an incorrect result.

  • A false positive pregnancy test means the test says you are pregnant, but you are NOT. [1]
  • A false negative pregnancy test means the test says you are NOT pregnant, but you are.
  • A faint line pregnancy test means you MAY be pregnant, but a more sensitive/accurate test is needed.

What causes inaccurate pregnancy test results?

  1. Insenstive Pregnancy Test
    Not all home pregnancy tests are created equal, even if they say 99% accurate. The manufacturer isn’t telling you that a test is more or less effective depending on how many days past a missed period you are. Pregnancy tests detect the hCG hormone levels in your body, which is a hormone produced right after implantation (the fertilized egg attaching to the wall of your uterus).  Your hCG levels then rise rapidly, doubling every two to three days for the next 10 weeks. [2] Thus, in the early stages of your pregnancy, your hCG levels are lower – and only the most sensitive pregnancy test can detect it. If a pregnancy test is showing negative or a faint positive line, this could be the result of a low-quality pregnancy test being unable to detect the lower hCG levels. Or, it could be a more sensitive pregnancy test triggering false positive lines because of other factors, such as the below.
  2. Improper Testing
    if you don’t follow the instructions exactly, it can give you an inaccurate result. Set a timer before reading the results – this is not a time to guess. Being off by just 30 seconds could give you a false result. Testing at least a week after a missed period will also give you more accurate results, as is taking the test in the morning when your urine is more concentrated.
  3. Medication Interference
    Some drugs like methadone, chlordiazepoxide, or promethazine can give you a false positive. Urine contaminated with blood or protein can also trigger a false positive.
  4. Medical Conditions
    Although very uncommon, it’s still possible to get a false positive because of hCG-producing medical conditions. These could include choriocarcinoma (rare form of cancer usually found in the uterus), breast, ovarian or testicular cancer.
  5. Defective Pregnancy Test
    It’s not common, but it’s not out of the question either. Check the expiration date.  And if you question the results, even on a non-expired test, it’s OK. Even with the highest quality control, there can be a defective test here or there. Try taking another test, or reach out to a local clinic such as Life Options for a laboratory-quality pregnancy test.

False positive and negative results (and faint lines) are not common, but they do happen. If you are unsure of your results, getting a laboratory-quality test is recommended.

We can provide you with a free lab-quality pregnancy test.  Our pregnancy tests are 99% accurate and more sensitive than home pregnancy tests. Our tests can detect the hcG pregnancy hormone as early as 7 days after conception or 21 to 24 days after the first day of your last period.

Schedule your free appointment today!




[1] http://www.babymed.com/pregnancy-testing/false-positive-pregnancy-test-result
[2] http://www.webmd.com/baby/guide/pregnancy-tests#1