False Negatives And
False Positives

Home pregnancy tests are really the best thing since sliced bread, but did you know that they are not always accurate?

Taking a pregnancy test

You’ve waited and waited, and now you can pop open that home pregnancy test and get an answer. Right? Well, yes, most of the time, but sometimes the answer you get isn’t correct after all.

False negatives

A false negative means that your test says “no” when you are actually pregnant. If you take the test at face value, you may not make nutrition or lifestyle changes that can give your child the best start in life.

Usually, the cause of a false negative is that you’ve taken the test too early. Best case scenario? You should wait until your period is late before testing. This is far easier said than done, especially for someone who has been trying to conceive for some time.

"Best case scenario? You should wait until your period is late before testing"

Most pregnancies can be detected the day your period is due using a standard home pregnancy test, but even then, false negatives can occur. There are pregnancy tests on the market that claim to give you an answer five or even six days before your period is even due, but taking a test that early means that you’re more likely to experience a false negative.

If your period is regular, and yours is missing, keep testing every few days. If some time passes, you might want to get in with a doctor who can help you determine if you’re pregnant or something else is keeping your period at bay.

False positives

Pregnancy tests

Far more rare is the false positive pregnancy test. A home test works by detecting the presence of the pregnancy hormone human chorionic gonadotropin (hCG). If it’s not present, then your test should be negative.

However, there are a few times where a test may show positive when you’re not actually pregnant.

Fertility treatment sometimes includes hCG injections to help trigger ovulation, and if you don’t wait long enough then you can be disappointed by a false reading. Your doctor should tell you when to expect the trigger to be gone, so keep that in mind as you test for pregnancy.

Certain illnesses, such as some types of cancers, can also contribute to a false positive. Some medications can do the same.

Evaporation lines are often initially thought of as false positives, but a general rule of thumb is that you must read the test results in a certain indicated timeframe -- and that’s it. Looking at it later may cause your heart to jump, but evaporation lines that pop up after the allotted time has passed, are not positive results.

Bottom line? Don’t test too early, and confirm positive results with a doctor as soon as you can get in.

More on pregnancy tests

History of the pregnancy test: A tale of two lines
How to take a home pregnancy test
Doubling times: Beta hCG pregnancy tests explained


recommended for you