Is It Possible To Get a False Pregnancy Test?

It’s natural to second-guess something as life-changing as a pregnancy test. You might even wonder, is it possible to get a false pregnancy test? There are several reasons why your test may not be as accurate as you thought. In fact, as much as 5% of all pregnancy tests report false-negative results.¹ We spoke to Dr. Jessica Ryniec of CCRM Fertility Boston, MD, Reproductive Endocrinology and Infertility, to understand what can cause false-negative and positive pregnancy tests.

How To Take and Read a Pregnancy Test

Before we address the causes of potential false positive and false negative pregnancy tests, we should first cover how to take a pregnancy test. For the best chance of accurate results from a pregnancy test, wait one to two weeks after missing your period before testing. Also, use urine from your first morning pee.² Here are the steps for taking a pregnancy test:⁸

1. Remove the plastic cap covering the absorbent window.
2. Sitting on the toilet, begin to urinate. Place the absorbent tip underneath your urine stream for eight to 10 seconds. (Alternatively, you can urinate into a small clean cup and dip the test’s absorbent tip into your urine for about 10 seconds.)
3. Replace the cap and lay your test flat.
4. After five minutes, check your results.

Remember not to leave your test too long, as this may cause a false positive!⁹ Now, here are three possible outcomes for your pregnancy test results:⁸

1. Positive result (possibly pregnant): You’ll see two bands in the control window — a band for the control and the test. The bands may be slightly faded or dark; in either case, it means the test is positive as long as both bands are visible. Depending on the hormone level, the test line is frequently lighter in color than the control line.
2. Negative result (not pregnant): Only the control line is visible, and there’s no colored band in the control window’s test region.
3. Invalid test: If no control line is visible, regardless of whether the test line is visible, this test is invalid. You should repeat the process above with a new test.

Causes of False-Positive Pregnancy Tests

It’s essential to ensure that your pregnancy test is free of user error. According to Dr. Ryniec, common user errors with pregnancy tests are:

• Not checking the “control” window to ensure the test is functioning correctly
• Using an expired test
• Leaving the test too long with urine on it
• Being on specific medications that can lead to a false positive (see below)
• Leaving your test at temperatures below 36 F or above 86 F
• Storing tests where they will have exposure to moisture, heat, or direct sunlight

Let’s explore some of the potential causes of false-positive pregnancy tests:

Biochemical Pregnancy

One of the most common causes of a positive pregnancy test that doesn’t result in a pregnancy is a biochemical pregnancy (or chemical pregnancy).¹⁰ These pregnancies occur when the sperm meets an egg, leading to an embryo that implants, but the pregnancy doesn’t progress. “Biochemical pregnancies can cause you to get your period just a few days to a week later than expected,” says Dr. Ryniec.

Ectopic Pregnancy

A similar cause of false pregnancy tests can occur when you experience an ectopic pregnancy. Ectopic pregnancies typically develop between weeks four and 12 of pregnancy, when a fertilized egg gets stuck on its way to your uterus, most commonly in the fallopian tubes.³ A fertilized egg can’t survive outside the uterus, leading to miscarriage. Ectopic pregnancies are rare, accounting for 1-2% percent of all miscarriages.⁴

It’s important to note that while rare, ectopic pregnancies are a health risk that can cause organ damage and death.⁵ If you’re concerned that you may be experiencing an ectopic pregnancy, speak to your healthcare provider immediately. The signs of an ectopic pregnancy include:⁵

• Severe abdominal pain
• Pelvic pain with bleeding
• Dizziness
• Shoulder pain

Other Causes

“You may also get a false-positive test if you are checking too soon after miscarriage or giving birth,” explains Dr. Ryniec. The pregnancy hormone hCG (human chorionic gonadotropin) level can stay elevated for up to six weeks after a miscarriage and can cause a false positive. Some medical conditions may also result in false-positive tests.¹⁰ Certain types of cancer, chronic kidney disease, or ovarian disease can cause false positives.^6,9,10 Finally, sometimes, women can have high levels of pregnancy hormones after menopause, and these elevated hormones can cause a false-positive test.^11,12

Causes of False-Negative Pregnancy Tests

False-negative pregnancy tests are another possibility, though they are also rare.¹ The user errors discussed above are common causes of false-negative tests. For example:^13,14

• Taking the test too soon
• Not providing enough urine for a proper sample
• Not using morning urine when the hCG hormone is the most concentrated
• Using a damaged or expired test
• Medications that can cause false negatives

Medications That Can Cause False Pregnancy Tests

Since home pregnancy tests measure levels of hCG hormone in urine, taking medication that contains hCG can cause a false-positive result.⁶ Drugs containing the hCG hormone that boost fertility may impact pregnancy test results. These may include:⁶

• Pregnyl
• Profasi
• Novarel
• Ovidrel

Other drugs that may cause a false positive pregnancy test include:⁶

• Antipsychotics often used to treat schizophrenia, such as perphenazine, prochlorperazine, chlorpromazine, trifluoperazine, thioridazine, and thiothixene
• The anti-seizure/anticonvulsant drug carbamazepine used for epilepsy, facial nerve pain, and bipolar disorder
• Progestin-only birth control pills, including:
  • Camila
  • Errin
  • Heather
  • Incassia
  • Jencycla
  • Jolivette
  • Micronor
  • Nor-Q.D.
  • Ovrette
• Anti-nausea drugs, including prochlorperazine, perphenazine, chlorpromazine, and promethazine
• Sedatives used before and after surgery or during labor, such as promethazine
• Antihistamines such as promethazine
• Anti-anxiety medications such as prochlorperazine and trifluoperazine

When In Doubt, Check With Your Doctor

At-home pregnancy tests have been on the market since 1976.⁷ But despite claims of tests being “over 99%” accurate, many over-the-counter pregnancy tests haven’t been tested in independent studies to prove their factual accuracy. Tools such as ultrasounds can give a much clearer picture of whether your pregnancy test result is accurate. Although using hCG as a marker for pregnancy is reasonably accurate, due to user error, faulty tests, and the possibility of failed pregnancies or medication causing inaccurate results, it may be necessary to visit your doctor to be sure of pregnancy.

We hope the information in this article helped you better understand how at-home pregnancy tests work and how to do them properly to avoid false results. Again, it’s helpful to talk to your doctor if you receive a positive test result.