Most home pregnancy tests, like Winx Health (formerly known as Stix), are over 99% accurate, but there is still that small chance you will get an inaccurate result. So what is the deal with inaccurate test results? What are they, why do they happen, and how can we do our best to avoid them? 

What can affect pregnancy test results?

It’s important to understand when to take a pregnancy test in relation to the day of possible conception. Pregnancy tests measure a hormone known as human chorionic gonadotropin, or hCG, that is produced by the placenta after a fertilized egg attaches to the uterine lining. The levels of hCG increase every single day post-conception so the longer you wait to test, the stronger and more accurate the results will be. Winx Health can detect hCG at 20mIU/hCG, or about 7 to 10 days after ovulation. For the best results though, we do recommend taking the test at least three days before your missed period or 19 days after you had sex. Additionally, taking a test first thing in the morning before you’ve had anything to drink will lead to more accurate results, less chance of a false negative pregnancy test, as your urine is more concentrated and will likely have higher levels of hCG. 

Taking birth control will not affect your chances of getting pregnant after you stop using it, nor will it affect your pregnancy test results when you are using it. The hormones in your birth control won’t impact the test’s ability to detect the hCG hormone. There are certain medications that may lead to false pregnancy test results, such as fertility treatments. A lot of fertility treatments work by providing synthetic hCG to help with ovulation, which could be mistaken by a pregnancy test as the real hormone. 

Drinking alcohol will not affect the results of your test. This being said, alcohol dehydrates you and might lead you to drink more water than usual, which could lead to a false negative result. Drinking too much water before taking a test will make it harder for the test to pick up traces of hCG in your urine. While alcohol doesn’t directly affect your results, it will directly affect your pregnancy so, as soon as you get a positive result, it’s time to stop drinking.

What causes a false positive pregnancy test?

False positives are much less common in pregnancy testing than false negatives. This is because it’s very rare for your body to produce hCG, the hormone that a pregnancy test detects, if you’re not pregnant. In a study that tested 27 different kinds of at home pregnancy tests, false negative results were displayed 48% of the time. 

The most common causes of false positives are traces of hCG in your urine that the test mistakes for pregnancy. As we mentioned, fertility treatments containing hCG might affect the accuracy of your results. Other medications that can increase the risk of a false positive include some anti-anxiety medications, antipsychotics, Parkinson’s disease medications, and antihistamines. Certain health conditions can cause your hCG levels to rise, even if you’re not pregnant, including ovarian cysts, kidney infections and UTIs, and pituitary gland disorders.

Additionally, taking a test too soon after a recent miscarriage or chemical pregnancy can detect hCG levels that have remained in your body. This test will show a positive result, but only because the pregnancy hormone is still in your body. Similarly, an ectopic pregnancy will most likely give you a positive test result. Ectopic pregnancies still produce the hCG hormone even though they are developed outside of the uterus. If you think you might be having one, see your primary care physician immediately. 

All tests are different, but false positives can be caused by problems with the test or issues interpreting your results. One likely cause of test misinterpretation is evaporation lines. On most pregnancy tests, a positive result is indicated with two lines and a negative result indicated by one line. An evaporation line looks like a faint, colorless line that appears to be a positive result. To avoid this, read your test instructions and wait to look at your results no earlier or later than they say to. Also, it’s important to make sure that your test is not expired. Expired tests aren’t as effective in detecting hCG levels and are more likely to produce inaccurate results.

False positive results in a blood pregnancy test are very rare, but possible. They are usually caused by medications that increase hCG in your blood such as hypnotics, Parkinson’s disease medicine, and medicine to prevent seizures. 

What do you do if you have an invalid pregnancy test result?

An invalid pregnancy test is not the same as getting a false result. Most at home pregnancy tests have two windows: a control window and a test window. If a line does not appear in the control window, the test is invalid. Even if a line appears in the test window, a blank control window means the test is invalid. 

If you get an invalid pregnancy test result, ignore whatever result it gives you. It’s likely that the test is either faulty or expired, or that there wasn’t enough urine on the test to produce a result. Check the expiration date on the box and, if they’re not expired, take a new one. If this keeps happening, try using a different brand and take more than one to confirm your results are accurate. Always remember to read the instructions and look at your results when they advise, not before or after.

Testing for pregnancy isn’t as simple as any of us thought! Winx Health is here to make it easier. Check out the Winx Health Library for tips and tricks on all things women’s health.