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7 Possible Causes For A False Positive Pregnancy Test
Updated on
- Written by Emma Garofalo, Former Health Writer
Medically reviewed by
Kimberly Langdon, MD
How rare is a false-positive pregnancy test? They‘re more common than you would think and much more common when you test positive at home.
Different medical conditions, straddling the line during your menstrual cycle, and taking fertility medications may all skew your results. If you’ve had a missed period and are hoping for a real answer as soon as possible, it’s best to rule out all the following possible causes of a false-positive pregnancy test.
What Is A False Positive Pregnancy Test?
There’s little more nerve-wracking than waiting for a read-out from a home pregnancy test. It’s a life-changing experience, and many home pregnancy tests claim that they’re up to 99% accurate.
Despite this, though, there is no denying that the convenience of at-home pregnancy urine tests does come at a cost. They’re not as accurate[1] as blood tests for pregnancy or a lab-analyzed urine sample—there is no lab involved, as the assay is chemically-driven and responds purely to the hCG levels your urine specimen exhibits.
What are some of the most common causes of a false-positive pregnancy test? Your false-positive results may be due to any of the following factors:
- Ectopic Pregnancy
- Chemical Pregnancy
- Molar Pregnancy
- Some Types of Medications
- A Recent Miscarriage or Abortion
- Reading the Test Incorrectly
- Taking the Test Incorrectly
There’s no way to distinguish a false-positive result from a truly positive pregnancy test in the moments after taking it. It may cause some women to panic. Before getting too worried, however, we recommend taking a step back.
We’ll dive into the finer details behind some of these worrisome false alarms below. First, though, we should clarify what an essay is and how they work in regard to at-home pregnancy tests.
How Does a Pregnancy Test Work?
Pregnancy testing at home relies on one vital compound[2] used to detect pregnancy—human chorionic gonadotropin (hCG), also known as the pregnancy hormone. Invented in 1977, they’ve been helping women take control of their reproductive life ever since.
hCG is generated by a woman’s trophoblast tissue, which is an important part of the placental system responsible for feeding the embryo and acts as a precursor to the placenta later on.
Suppose you’ve ever taken a pregnancy test. In that case, you’re already familiar with the plastic cassette casing, the well upon which you’re expected to urinate, and the tiny read-out window where you’ll inevitably wait to see your results develop.
Pregnancy tests work, above all else, only if they’re given an accurate representation of your bodily state at the time of the test through the urine specimen you present it with. If any outlying factors change the quality or character of your urine sample—diluting it by drinking a ton of water beforehand, for example—you’re subject to a reading that doesn’t apply to you.
Both a false-positive reading and even a false-negative result can distress a pregnancy test-taker unduly. For this reason, we recommend following the instructions on your at-home pregnancy test to the line, no pun intended.
Causes of a False Positive Pregnancy Test
Even if your home pregnancy test results come up positive, there’s still some degree of uncertainty you should be taking into consideration.
Read on and ascertain whether any of the following are relevant to your situation. If you have second thoughts about the accuracy of a positive or negative result, we recommend consulting a medical professional as soon as possible.
1. Ectopic Pregnancy
When a fertilized egg attaches itself to a fallopian tube or another structure in the pelvis instead of to the lining of the uterus, the problem is called an ectopic pregnancy. The zygote never makes it to the safety of the womb, resulting in early pregnancy loss. If the ectopic dissolves, then the urine test will turn negative eventually. However, if it stays positive and there is no evidence of an intrauterine pregnancy, then your doctor will advise you of your options. Ectopic pregnancies can rupture and be deadly.
2. Chemical Pregnancy
Chemical pregnancies are an early pregnancy that does not come to fruition—at one point, sperm may have come together to form a zygote with one of your eggs, and, in some cases, the fertilized egg implants itself to some extent before it ultimately fails to develop so the pregnancy disappears.
When chemical pregnancy occurs, your body may produce hCG at levels sufficient enough to cause a false-positive test result. If you’ve missed an expected period, but a blood test indicates that you’re not pregnant later, this may very well be the reason.
3. Molar Pregnancy
A hydatiform mole or a molar pregnancy is a gestational trophoblastic disease[3] (GTD). Basically, it’s a malignant tumor of the placenta that arises from one’s gestational tissue, as opposed to the tissue of the mother.
When this happens, a woman’s hCG hormone levels elevate, even if no embryo is present in the womb at the time. It’s a life-threatening condition that requires immediate medical help and even a hysterectomy in some extreme cases.
4. Some Types of Medications
What medications cause a false positive pregnancy test? Weight loss drugs, aspirin, fertility treatments, carbamazepine, and methadone can all toy with your body’s natural hormone levels and can all cause false positives.
Many types of fertility drugs will cause elevated beta hCG levels or free-floating hCG in the blood because they contain synthetic hCG. The urine test will detect hCG, which results in a false-positive test in many cases.
5. A Recent Miscarriage or Abortion
If you’ve had a miscarriage, an abortion, or even a successful delivery recently, the levels of hCG in your body may actually still be high enough to yield a false-positive result.
This is probably one of the easiest ways to rule out a positive result that doesn’t feel accurate. If you’re not sure, consult your physician for a full panel.
6. Reading the Test Incorrectly
It is imperative that you’re familiar with your test’s read-out guidelines—ensuring you are will help you prevent a stressful misunderstanding. The complete range of commercially-available home pregnancy tests is all different, though. Here’s how to read an ordinary pregnancy test stick easily.
For a single-window test, you’ll have two lines to look out for: a test line that assures you that the test is viable and functioning and a positive line, which is your indicator of a positive test.
Once the test line appears after being exposed to your urine stream, this second line indicates a positive result. If only the test line appears after the urine test, you’re probably not pregnant.
Like two-window and digital tests, other tests may differ slightly, but the gist will remain largely the same. Read the instructions thoroughly, and find more help online if you have any questions on how to read a positive test result.
7. Taking the Test Incorrectly
Can you get a false positive pregnancy test by taking the test improperly? Absolutely, and it might be easier to do so, thank you think.
No matter what pregnancy test brand you choose, you should read the instructions first thoroughly before you start to take the test. Following these guidelines is the best way to avoid a false negative pregnancy test if none of the above apply to you.
The Bottom Line
It’s tough to live normally when something as important as this isn’t a sure thing. If you test positive for pregnancy under any circumstances, we recommend seeking the help of a healthcare professional able to provide a more concrete result.
If you’re hoping to conceive, see your doctor the second you test positive under any circumstances. They’ll be able to give you more guidance on how to find success as a new mother.
+ 3 sources
Health Canal avoids using tertiary references. We have strict sourcing guidelines and rely on peer-reviewed studies, academic researches from medical associations and institutions. To ensure the accuracy of articles in Health Canal, you can read more about the editorial process here
- Gnoth, C., & Johnson, S. (2014). Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments. Geburtshilfe und Frauenheilkunde, 74(7), 661–669. https://doi.org/10.1055/s-0034-1368589
- Vaitukaitis J. L. (2004). Development of the home pregnancy test. Annals of the New York Academy of Sciences, 1038, 220–222. https://doi.org/10.1196/annals.1315.030
- Ghassemzadeh, S., Farci, F. and Kang, M. (2022). Hydatidiform Mole – StatPearls Publishing, p. Available at: https://www.ncbi.nlm.nih.gov/books/NBK459155/
Written by:
Emma Garofalo, Former Health Writer
Medically reviewed by:
Medically reviewed by:
