June 15, 2024

If a woman is trying to conceive or suspects she may be pregnant, home pregnancy tests can be bought at pharmacies and many stores selling personal hygiene items.

Although many home pregnancy tests claim 99 percent accuracy, they are not perfect. A false-positive result is one where the test indicates that the user is pregnant when she is not.

Several factors can lead to a false-positive or negative reading. This article discusses some of the potential causes of a woman getting a false-positive pregnancy test reading.

How does home pregnancy tests work?

Home urine pregnancy tests work by detecting the presence of human chorionic gonadotropin or hCG in the urine. This is the hormone of pregnancy, and it is found in both the urine and blood.

Home pregnancy tests vary depending on the brand, and each one will have detailed instructions to follow for accuracy.

Some kits require the user to place a test stick in her urine stream. Others may use a urine collection cup to either dip a pregnancy stick in or to retrieve urine from with a dropper for placement on the test stick.

The way the test reveals a positive or negative result also depends on the brand and can include:

a plus or minus sign
the word or words “pregnant” or “not pregnant”
one or two indicator lines
Importantly, when taking a pregnancy test, a woman should be aware that even a faint plus sign or a line indicates a positive result.

However, not all positive pregnancy tests mean that a woman is pregnant. There are some occasions when a pregnancy test can give a false-positive reading.

People should speak with their doctor for further evaluation if they receive a positive pregnancy test.

Also, it is important for a woman to speak with a medical professional if she believes she may be pregnant, but she has received a negative pregnancy test. This is because further testing may be necessary to confirm her condition correctly.

Listed below are five possible situations which could cause a woman to have a false-positive result from a home pregnancy test.

Evaporation lines

When taking a home urine pregnancy test, it is important to follow the test’s instructions fully. Each brand has specific instructions, so it is vital to read them closely.

Most tests will ask the user to read the result within 4–5 minutes of taking the test and no longer than 10–30 minutes afterwards.

Most non-digital urine pregnancy tests will show one line if a woman is not pregnant and two lines if she is pregnant, or a plus or minus sign.

If the pregnancy test is read after the recommended time has elapsed, it may result in what looks like a positive test result. However, in most cases, this is not a positive pregnancy test but an evaporation line left by the urine after the recommended time for reading the test


Certain medications may lead women to have false-positive pregnancy tests.

These medications include those with hCG as an active ingredient, which is often used to treat infertility. A person who is taking medication to treat infertility may wish to be tested for pregnancy by their doctor.

Most medications and drugs, including alcohol, do not affect the results of home pregnancy tests.

Medical History

Certain medical conditions can cause a woman’s hCG to rise, even when she is not pregnant. They include:

  • disorders affecting the pituitary gland and hormone levels, specifically in perimenopausal or menopausal women
  • gestational trophoblastic diseases, which cause tumours in the cells that would normally make up the placenta
  • cancers of the ovary, bladder, kidney, liver, lung, colon, breast, and stomach
  • phantom hCG, where antibodies interfere with the testing kit
  • ovarian cysts
  • kidney disease or urinary tract infections

Phantom hCG occurs when certain antibodies bind with the molecules in the pregnancy testing kit that are used to detect hCG. The interaction causes the testing kit to signal that hCG levels are higher than they actually are.

What to do if the pregnancy test is possible

If someone has a positive pregnancy test, it is important to notify their doctor, as they will need further evaluation and testing to confirm and monitor their pregnancy.

If someone believes that they may be pregnant, but their home pregnancy test results are negative, they should speak with a doctor for further guidance.

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