Can You Get a False Negative Pregnancy Test Result?

If you've missed your period, a negative pregnancy test result can be confusing. Whether you're using contraception or actively trying to conceive, you might be wondering, "Is it possible to get a false negative pregnancy test?" As it turns out, the answer is yes.

Home pregnancy tests are very reliable, but false negatives are possible. They might happen if your body hasn't produced enough pregnancy hormone for the test to pick up. Other factors, ranging from a faulty test to certain medical conditions, might also be to blame.

Keep reading to learn more about false negative pregnancy tests, including what causes them and what to do if you're doubting the results.

How Do Home Pregnancy Tests Work?

At-home urine pregnancy tests are designed to detect the presence of human chorionic gonadotrophin (hCG), which is a hormone that's only produced during pregnancy. To use a home pregnancy test, a person pees on a stick containing a reactive paper that's able to detect whether there's hCG. Within a few minutes or less, a negative or positive result is shown.

How Accurate Are Pregnancy Tests?

Many home pregnancy tests claim to be 99% accurate. But the accuracy of the test depends on a host of factors, including how far along a person is in pregnancy when they take the test.

“Depending on the brand and specific test type, there are different detection thresholds for the hormone,” explains Alan Copperman, MD, FACOG, an infertility specialist, managing director and CEO of RMA New York, and medical advisory board member at Progyny.

Urine pregnancy tests are not as accurate as blood pregnancy tests, which are given in a health care provider's office. These can pick up even a slight level of hCG in a person’s blood. “While blood tests can detect levels as low as 5 mIU/ml, the most sensitive urine tests can only pick up the presence of hCG if it's closer to 20 mIu/ml or more,” explains Janet Choi, MD, board-certified reproductive endocrinologist and chief medical officer for Progyny.

Reasons for a False Negative Pregnancy Test Result

Home pregnancy tests are generally very reliable when taken following manufacturer instructions. But incorrect pregnancy test results are possible, and false negative results are slightly more common than false positives.

If you've just received a negative pregnancy test result but strongly suspect you may actually be pregnant, here are some reasons you could be right.

The test was taken too early

"If a pregnancy test is taken too early, a test can look negative when a woman is really very early in her pregnancy,” explains Comfort Ughanze, MD, an OB-GYN and assistant professor at McGovern Medical School at UT Health Houston.

There is a wide range of "normal" when it comes to hCG levels, but the earlier you test, the more likely it is that your body isn't producing enough hCG to trigger a positive test result at home.

For people with irregular cycles, testing too early is even more likely as it can be difficult to know when ovulation occurred and when the next period was due.

The test was taken too late

A rare, counterintuitive cause for a false negative is that you are actually too far along in your pregnancy. If, for example, your period is weeks to months late, a pregnancy test might come up negative thanks to something known as the variant hook effect.

The results were read too soon

If you check too early, the test may not have absorbed enough hCG from your urine to turn the color of the test strip, and you might see a negative result even if you are pregnant. False positives, on the other hand, are more common when reading test results too long after directed. Be sure to follow the test instructions carefully.

The test was expired or faulty

Don't use a pregnancy test that is past its expiration date, says the Food and Drug Administration (FDA). Old tests can become less sensitive to hCG levels in your urine, which can cause a false negative result.

You are pregnant with multiples

An unusual but possible reason for a false negative is that you’re expecting twins or other higher-order multiples. In this case, a false negative pregnancy test can be caused by what is known as the "hook effect."

Your body produces higher levels of hCG if you are pregnant with multiples than if you have a singleton pregnancy. With the hook effect, unusually high levels of hCG can cause a urine pregnancy test to give a false positive reading.

You have a molar pregnancy

Another uncommon cause of a false negative test is gestational trophoblastic disease (GTD), a spectrum of pregnancy-related disorders that includes molar pregnancy. In a molar pregnancy, a tumor grows in the uterus early in pregnancy, preventing the placenta from developing.

GTD leads to extremely high levels of hCG, leading to the hook effect that can throw off urine-based pregnancy tests. Unfortunately, a molar pregnancy almost always ends in pregnancy loss.

You have an ectopic pregnancy

In rare cases, an ectopic pregnancy can cause a false negative test result. An ectopic pregnancy is when the embryo implants somewhere other than the uterus such as a fallopian tube.

These pregnancies don't develop properly and the formation of the placenta is delayed, which impedes the production of hCG. This disruption in hCG production can affect home pregnancy test results.

What To Do After a Negative Pregnancy Test

If you've gotten a negative pregnancy test but think you may be pregnant, you can repeat the test in two to three days. Or you can head to your health care provider for a more reliable blood test.

Always make sure to get support from a loved one or medical professional if you're having a hard time dealing with the results of your pregnancy test.

Reasons for a Late Period Other Than Pregnancy

If your period is one to two weeks late and you still are getting negative pregnancy tests, a visit to a health care provider for a pregnancy blood test is recommended to rule out complications.

The most common reason for a late period and a negative pregnancy test is that your period is simply delayed that cycle. Having one or two irregular cycles a year is not unusual and doesn't necessarily mean there is anything wrong. "Missed periods can occur for many different reasons besides pregnancy," confirms Dr. Ughanze. 

Some reasons you may miss a period despite not being pregnant include:

• Stress
• Poor sleep
• Excessive exercise
• Changes in weight
  
• Hormonal contraception (such as birth control pills, vaginal rings, etc.)
• You’ve been traveling
• Illness
• You’re menopausal or perimenopausal
• You're breastfeeding

If you have a pattern of delayed periods, it's best to be evaluated by a health care provider. Delayed periods can be caused by thyroid disorders or other medical conditions, like polycystic ovary syndrome (PCOS), a hormone imbalance that causes irregular ovulation. Irregular cycles can be a risk factor for infertility.