12 Reasons For False Positive Home Pregnancy Tests

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A home pregnancy test (HPT) is often useful to know about pregnancy immediately. Many women prefer this test since it provides you with the answer in the privacy of your own house. But what if we told you that there are chances of experiencing a false-positive home pregnancy test result?

Yes, this is possible and may lead to lots of confusion. While false-positive results are extremely rare, they do happen, and there might be various reasons behind them.

Keep reading this post to learn more about HPT, as well as some of the reasons for false-positive results and how to avoid them.

How Does HPT Work?

Before you try and understand why you can get a false home pregnancy test, it is first important to comprehend how an HPT works.

When you are pregnant, your body produces a hormone called Human Chorionic Gonadotropin or hCG. A home pregnancy test checks for this very hormone in your body. If there is a substantial amount of hCG in your body, it passes on to your urine and gives you a positive pregnancy test (1).

Why Does A False Positive Home Pregnancy Test Happen?

A false positive, or a positive HPT without being pregnant is rare. But when it does happen, the following reasons may be at work:

1. Fertility Treatment:

Infertility can be devastating. And if you get a false positive while you are struggling to conceive, it can almost break your spirit. But if you are undergoing fertility treatment that requires hCG shots, it is possible to get a false positive. It is because the HPT ends up detecting the remnants of the hCG shot in your body (2).

2. Evaporation Line:

Some pregnancy tests leave an evaporation line when the urine runs across the test strip. Usually when the urine passes, it changes in color, thereby helping you locate the test results. If the test in positive, it will change in color and have a line at the proper testing time. But if you observe no line and it requires to manipulate the light to observe the line properly, it may be an evaporation line. It can also happen when you end up seeing the result after 10 minutes (3).

3. Improper Testing:

Most women who show a positive pregnancy test will be pregnant and a few are not. The primary cause of a false positive pregnancy test is that you may not read the test correctly. Pregnancy home tests will have certain instructions that you need to follow correctly. It is important to read the manufacturer’s instructions before taking a pregnancy test. Most test kits require you to read the test after exactly 3 minutes and not to read if it crosses 10 minutes. Once you read the test to be negative after 3 to 5 minutes, you should throw away the test. Any positive test that shows after the time goes inaccurate cannot be considered right (3).

It is very important to follow the instructions given on the HPT. If you fail to do so, you may end up getting your hopes up only to see them break into pieces later!

4. Chemical Pregnancy:

It is one of the most heartbreaking causes for a false positive. For the briefest of moments, your body is pregnant. But the fetus fails to latch on to the uterus. All this happens, many times, before you miss your period. Many times, what many women consider to be a late period is the end of a chemical pregnancy. Your chances of getting a false positive due to a chemical pregnancy go up if you test before your period date (4).

5. Certain Medical Conditions:

Though it is not common, some medical conditions can cause a false positive pregnancy result. Ectopic pregnancy, menopause, ovarian cysts and some rare medical conditions can give misleading results. Certain forms of cancers like choriocarcinoma (cancer found in the uterus), breast, ovarian and testicular cancers can produce hCG leading to a false positive result (5).

6. Medications:

If you are taking certain medications, such as methadone, chlordiazepoxide, or promethazine, you may experience false positive pregnancy tests (3). Women receiving hCG shots or any other fertility treatment should consult their health care provider about the accuracy of the home pregnancy tests. The reason is the medications can interfere with the test results by contaminating the urine with blood or gross amounts of drugs.

7. Faulty Pregnancy Test:

Before you use an HPT, check its expiration date. Many false positives are a result of tests that had passed their use by time. Many times, you may just end up with a faulty pregnancy test, which can give false positives.

8. Contaminated Urine Sample:

Some pregnancy test kits usually come with cups. Washing the cup may contaminate the urine sample if you do not wash all the soap or detergent before the test. You should note that these cups are sterile and do not require any washing before using them.

9. Pituitary hCG:

The human pituitary gland produces low levels of hCG (6). The hormone is more commonly detected in menopausal women. So, if you are over 40 and get a false pregnancy test, you can blame your pituitary gland for it!

10. Tubo-ovarian Abscess:

Some women with tubo-ovarian abscess too can experience false positive HPTs (7). Women who are suffering from pelvic inflammatory disease often experience this serious health issue.

11. Antibodies:

Some women possess antibodies in their blood, such as heterophile antibody, that can interfere with an HPT and give false positives (7).

12. Hemodialysis:

If you are suffering from a renal disease and undergoing Hemodialysis, you may experience a case of a false positive pregnancy test (8).

How To Avoid A False Positive Test Result?

False positive pregnancy results are rare. Most of the health experts recommend going for at least two home pregnancy tests to confirm your pregnancy. Trying different brands can reduce the likelihood of misreading the results.

Most home pregnancy tests show 99% effective results if you follow the directions correctly. But you should also remember that the positive test can be misleading sometimes. Also, the time you take the test plays a huge difference. It would be best if you wait until you have missed a period and then take the test. Taking the test in the morning gives accurate results since hCG levels are highest in the morning time.

Frequently Asked Questions

1. Can a UTI cause a false positive pregnancy test?

Yes. Severe urinary tract infections with high levels of white blood cells (WBCs), red blood cells (RBCs), and nitrite can occasionally result in a false positive pregnancy test (9).

2. How many pregnancy tests should I take after a positive?

If you get a positive pregnancy test result, you usually don’t need to repeat the test because home pregnancy test kits have a 99% accuracy rate. You can directly make an appointment with an obstetrician. However, many women choose to repeat the test just to be sure.

3. Can hormonal imbalance cause false positive pregnancy tests?

Yes. Hormonal imbalance of hCG due to factors such as ectopic pregnancy, pituitary hCG in menopausal women, miscarriage, trophoblastic disease, and phantom hCG may result in a false positive pregnancy test (10).

4. Can kidney stones cause a false positive pregnancy test?

Yes. A case study conducted by Rahul Mital et al. (2020) reported that false positive pregnancy tests could be associated with obstructive pyelonephritis caused by kidney calculus (kidney stone) (11).

Although uncommon, false-positive pregnancy results occur, especially when using a home pregnancy test kit. Fertility treatments, inadequate testing, faulty test kits, contaminated urine samples, certain drugs, and medical conditions can impact a false-positive home pregnancy test result. If you want to avoid false positives, follow the directions while taking the test, don’t keep the test, and throw it away if it shows a negative result. Also, if you believe the test is inaccurate, make an appointment with a gynecologist to double-check the result.

Infographic: Avoid Getting A False-Positive Pregnancy Test

A false-positive pregnancy test may lead to unnecessary confusion and diagnosis. Therefore, it is essential to take precautions and get an accurate result. This infographic shares with you some ways of avoiding an inaccurate pregnancy test.

ensuring the accuracy of a pregnancy test [infographic]
Illustration: MomJunction Design Team

References:

MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
  1. Pregnancy Tests.
    https://www.plannedparenthood.org/learn/pregnancy/pregnancy-tests#:~:text=Pregnancy%20tests%20work%20by%20checking
  2. Causes of a False Positive Pregnancy Test.
    https://health.clevelandclinic.org/false-positive-pregnancy-test/
  3. 7 Reasons Your Pregnancy Test Gave A False-Positive.
    https://www.thesource.org/post/reasons-your-pregnancy-test-gave-a-false-positive
  4. Carolyn B Coulam and Roumen Roussev; (2002); Chemical pregnancies: immunologic and ultrasonographic studies.
    https://pubmed.ncbi.nlm.nih.gov/12516655/
  5. Ulf-Håkan Stenman et al.; (2004); Human chorionic gonadotropin in cancer.
    https://pubmed.ncbi.nlm.nih.gov/15234236/
  6. Final Diagnosis — Pituitary hCG production.
    https://path.upmc.edu/cases/case824/dx.html
  7. M E Levsky et al.; (2001); False-positive urine beta-HCG in a woman with a tubo-ovarian abscess.
    https://pubmed.ncbi.nlm.nih.gov/11728769/
  8. A Schwarz et al.; (1985); Value of human chorionic gonadotropin measurements in blood as a pregnancy test in women on maintenance hemodialysis.
    https://pubmed.ncbi.nlm.nih.gov/2580246/
  9. Pregnancy test (beta-hCG).
    https://www.gloshospitals.nhs.uk/our-services/services-we-offer/pathology/tests-and-investigations/pregnancy-test-beta-hcg
  10. Jennifer Goldstein et al.; (2016); A non-pregnant woman with elevated beta-HCG: A case of para-neoplastic syndrome in ovarian cancer.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910296/
  11. Rahul Mital et al.; (2020); A Case of a False-Positive Urine Pregnancy Test and Delayed Diagnosis of Obstructive Pyelonephritis.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7117853/
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shreeja pillai

Shreeja holds a postgraduate degree in Chemistry and diploma in Drug Regulatory Affairs from the University of Mumbai. Before joining MomJunction, she worked as a research analyst with a leading multinational pharmaceutical company. Her interest in the field of medical research has developed her passion for writing research-based articles. As a writer, she aims at providing informative articles on health... more

Dr. Deepti Gupta

(MS)
Dr Deepti Gupta graduated in medicine from Mumbai and pursued post graduation in Obstetrics and Gynecology from Gwalior. She worked in Gandhi Medical College Bhopal before settling in Jabalpur, Madhya Pradesh. She has been practicing obstetrician/ gynecologist since 2008 with special interest in infertility reproductive health.    Currently, Dr. Gupta is an assistant professor in the department of Netaji Subhash... more