Can You Get a False Negative Pregnancy Test?

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 in rare occasions. They might happen when your body hasn't produced enough pregnancy hormone (hCG) for the test to pick up. Other factors—such as user error or an expired test—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?

Urine pregnancy tests detect the hormone known as human chorionic gonadotrophin (hCG), which is 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 in the urine. 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 accuracy depends on a host of factors, including how far along a person is in pregnancy when they take a urine test at home.

“Depending on the brand and specific test type, there are different detection thresholds for the hormone,” explains Alan Copperman, M.D., FACOG, an infertility specialist, managing director and CEO of RMA New York, and medical advisory board member at Progyny. “For example, some results for pregnancy tests read positive when the hCG is greater than 50 miu/mL, and others are more sensitive.” 

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, M.D., board-certified reproductive endocrinologist and chief medical officer for Progyny.

Pregnancy tests may show a positive result if they are performed two weeks after ovulation. But it’s best to take a home pregnancy test after a missed period.

What Can Cause a False Negative Pregnancy Test?

Some urine pregnancy tests can detect a pregnancy as soon as six days before a missed period, but there can be slight variations. 

"If a pregnancy test is taken too early, the test can look negative when a woman is really very early in her pregnancy. This is called a false negative,” explains Comfort Ughanze, MD, an OB-GYN and assistant professor at McGovern Medical School at UT Health Houston. “If possible, it's best to wait until after a missed period" before taking a pregnancy test.

Dr. Ughanze explains that other common reasons for a false negative pregnancy test include:

• Taking the test incorrectly
• Using an expired test
• Miscalculating your menstrual cycle
• Testing at the wrong time of day (For most accurate results, take the test first thing in the morning when your urine is most concentrated)

Rare Causes of a False Negative Pregnancy Test

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. This usually occurs in the fallopian tubes, but it can also happen elsewhere.

An ectopic pregnancy does not develop properly and is not viable. The formation of the placenta is delayed which impedes the production of hCG. An ectopic pregnancy can be dangerous if it causes the fallopian tube to rupture.

Ectopic pregnancies are rare, occurring in around 1 in 40 pregnancies. However, they can be fatal. Around 9% of pregnancy-related deaths are caused by an ectopic pregnancy.

Another rare cause of a false negative test is gestational trophoblastic disease (GTD), more commonly known as a molar pregnancy. GTD is a rare type of tumor that forms from a developing embryo. In less than 1 in 100 cases, a healthy baby can develop from a molar pregnancy. Usually, however, a molar pregnancy ends in miscarriage.

GTD causes extremely high levels of hCG. As mentioned above, elevated levels of hCG can throw off an at-home pregnancy test and give a negative result. While GTD is a tumor, it’s rarely cancerous. The treatment is usually having a D&C. If pregnancy hormone levels remain high, chemotherapy might be needed.

Pregnancy Test Errors

A false negative can also occur due to test errors. If you wait too long to read the results, you might get a false negative. That said, false positives are more common when reading a test too late. Make sure that you follow the directions of the particular pregnancy test you purchased. To avoid confusion, be sure to read the result within the time window recommended.

Another possible cause of a false negative is an expired test. Storing the test improperly (for example, in a damp, hot bathroom cabinet) can also cause it to malfunction.

Rare Causes of Pregnancy Test Malfunction

A rare, counterintuitive cause for a false negative is that you are too far along in your pregnancy. For example, if your period is weeks to months late, a pregnancy test might come up negative. This is called the variant hook effect.

Another unusual but possible reason for a false negative is that you’re expecting triplets or even twins. In this case, a false negative pregnancy test can be caused by what is known as the high dose hook effect. Ironically, unusually high levels of hCG can cause a pregnancy test to give a false negative result.

A very rare cause of a false negative pregnancy test is when the hCG hormone in your body does not react with the anti-hCG chemicals in the test. In this case, you might need to wait a few more days before you can get a positive result or need to have a blood test.

Can Too Much Pee on a Pregnancy Test Make It Negative?

Urinating too much on a urine pregnancy test should not cause a false negative result. But diluted urine, or urine with a higher water content, can impact a pregnancy test by skewing results. “A general tip I like to share with my patients is that the first morning urine is often the best time to test because it is likely the least diluted,” explains Dr. Cooperman.

Can I Be Several Weeks Pregnant and Still Test Negative?

Yes, that can be possible, but it’s rare. The likely cause is variations in a person's menstrual cycle. For example, "some women might think they are five weeks pregnant but are really only four weeks pregnant," says Dr. Ughanze. "If a woman tests too early, the result can be falsely negative."

The bottom line: It's highly recommended to take a pregnancy test at the right moment. That's typically after a missed period and testing with urine first thing in the morning. This will give you better chances of getting an accurate result.

What Can Cause a Late Period and Negative Result if You’re Not Pregnant?

The most common reason for a late period and a negative pregnancy test is that your period is simply delayed and you’re not pregnant. Having one or two irregular cycles a year is not unusual and does not mean there is something wrong. "Missed periods can occur for many different reasons besides pregnancy," confirms Dr. Ughanze. 

Some reasons you may miss a period—but not be pregnant—include:

• Stress
• Poor sleep
• Too much exercise
• Changes in weight
• Thyroid disorders or other medical conditions
• PCOS, a hormone imbalance due to lack of or irregular ovulation
• Birth control methods (such as birth control pills, vaginal rings, etc.)
• You’ve been traveling
• Illness
• You’re menopausal or perimenopausal
• You're breastfeeding

Dr. Ughanze says if a person is missing their periods and is not pregnant, it's best to be evaluated by a health care provider.

What Should You Do After a Negative Pregnancy Test?

If you've gotten a negative pregnancy test, but you're suspicious about the results, you can repeat the test in two to three days. Or you can head to your health care provider for a quantitative blood test, which measures the exact amount of hCG in your blood.

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.

When to Contact a Health Care Provider

If your period is one to two weeks late, and you still are getting negative pregnancy tests, a visit to an OB-GYN or health care provider for a pregnancy blood test is recommended. If your periods are frequently irregular, talk to your provider about when they’d like you to call. Depending on your circumstances, many providers will want to induce a "period" if you go more than two or three months without menstruating.

If your cycle used to be regular but has become irregular, or your periods are irregular for more than three months after stopping birth control, you should see your provider. Irregular cycles can be a risk factor for infertility.

Additional reporting by Rachel Gurevich, RN.