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False positive pregnancy test

Market is full of modern home pregnancy tests and women are often very much confused which pregnancy test is the best. The answer is very simple – just read the instruction and choose the most sensitive test (able to detect small concentrations of hCG), with normal expiration date, with 97-99% accuracy and easy to use.

All pregnancy tests come with special guidelines, enabling accurate detection of the results. The change in color is due the presence of the hormone Human Chorionic Gonadotropin (hCG) in the urine – this hormone acts like a marker confirming the pregnancy.

Accuracy of pregnancy tests is 97-99% but what about the rest? – 1-3%? The answer is simple – in 1-3% cases you could have false pregnancy test. In most cases you could have false negative pregnancy test but sometime it could be FALSE POSITIVE PREGNANCY TEST.


Positive pregnancy test means the test detected certain concentration of so called “pregnancy hormone” – Human Chorionic Gonadotropin (hCG).

Usually placenta starts secretion of the hCG immediately after the embryo implants into the uterine wall and from that moment the amount of hCG will increase exponentially in the first weeks of pregnancy.

Non-pregnant women also could have certain concentration of hCG in the blood (under 5 mIU/ml) but home urine pregnancy tests cannot detect such a small concentration of the hormone. Therefore, a positive result will appear if and only if the test detects enough hCG to indicate pregnancy (above 25mIU/ml).


Missed period

You missed your period and ready to take the pregnancy test. When is the right time for pregnancy test?
According to instructions some pregnancy tests could be done even before missed period but at that time the possibility for false pregnancy test is pretty high.

Usually pregnancy test could give positive results within 14 days after conception.

It is recommended to use pregnancy test after missed period (few days).

Evaporation Lines

Evaporation line on a pregnancy test can also cause a false positive pregnancy test. You should be careful with urine evaporation lines which could be confused with positive pregnancy test. Sometimes the urine passing through the strip leaves very faint line on pregnancy test – it could briefly change the color of the strip. Actually the evaporation line occurs on home pregnancy test kit when the urine sample begins to dry on the test kit. The best way to not let this evaporation line and false positive test confuse you is to read pregnancy test result within the stipulated time as mentioned in the pregnancy test instructions.

Pregnancy test instructions usually request that you read the results of the test within a given time frame (in most cases after 5 minutes). The reason for this is so that you do not confuse the appearance of urine evaporation lines with false positive test line.

Fertility treatment with hCG

Positive Pregnancy Test

Human Chorionic Gonadotropin (hCG) is not only produced in the female body but it also could be produced by pharmaceutical companies (as a medicine used for several health conditions). Very often fertility specialists recommend shots of hCG to stimulate ovulation (in cases of infertility with anovulation). In non-pregnant women body the hCG acts like luteinizing hormone and helps to rupture the follicle – to insure the ovulation.

Depending on the dosage, the hCG could be detected in the blood up to two weeks after the shot which also could provoke false positive pregnancy test.

For avoiding the false positive pregnancy test women with hCG shots can take the pregnancy test ONLY after 14 days if the shot was 10,000 IU; after 10days if the shot was 5,000 IU and after 7 days if the shot was 2,500 IU.

Wrong testing – wrong interpretation

The common reason that can lead to a false positive pregnancy test is incorrect testing (wrong process, wrong interpretations). It’s very important to read pregnancy test guidelines provided with the test before performing the test.

Many women are very impatient to discover the final result of the pregnancy test (both in positive and negative cases). If you would like to avoid false positive pregnancy test, just follow all instructions and read test results on recommended time and manner. Any mistakes could provoke false results.

Missed reaction time

In many cases women are missing the reaction time while doing pregnancy test. You should read the pregnancy test’s results within the stipulated time (not earlier and not later!). If you let the reaction sit for a longer time, the test will become invalid. Sometimes, you do not know how to read a pregnancy test and you spend a lot of time analyzing the reaction. This might lead to change in color showing a false positive result.


Drugs interference is also very important for correct pregnancy tests. Some medications (anti-convulsants, medications to treat Parkinson’s disease, certain tranquilizers, and certain diuretics) could be a reason for false positive pregnancy test.

Before starting the pregnancy test just evaluate all medication used during last months.

Chemical Pregnancy

“Chemical pregnancy” is a very specific terminology for very early miscarriages which women even don’t know and/or don’t feel. In such circumstances, women get a positive result due to the high sensitivity of the pregnancy kit but later they might end up with menstrual bleeding. Chemical pregnancy actually means – you did in fact conceive successfully but unfortunately experienced a very early miscarriage.

Sometimes false positive pregnancy test can also predict an early miscarriage (known as “chemical pregnancy”). Fertility specialists suggest that up to 70% of conceptions end in very early miscarriage. Many women experience a chemical pregnancy without ever realizing it, as the miscarriage occurs soon after conception and the menstrual period arrives on time.

Molar pregnancy – Trophoblastic tumors

This kind of tumors can grow in women’s reproductive system and they can provoke false pregnancy positive test. The main reason for false pregnancy test is increased volume of hCG produced by trophoblastic tumors. These tumors can also provoke false pregnancy symptoms – morning sickness, swelling in the abdomen, strange feelings, etc.

Early diagnostics of trophoblastic tumors is a guarantee for successful treatment. Check also Molar Pregnancy.

Some diseases of the liver, cancers such as choriocarcinoma that is an extremely rare type of cancer found in the uterus can cause the hCG level in the body to shoot up. Some types of breast cancers and ovarian cancers can also cause a false positive pregnancy test.

Expired date and bad quality

As any product in the market, pregnancy tests also can have different kinds of quality, accuracy and expiration dates. Just be careful and check the quality of the product – read instructions, expiration date and accuracy indications.

False Positive Pregnancy Blood Test

Pregnancy blood test is different from ordinary home pregnancy tests. Blood pregnancy test is usually more accurate (about 99%) because of test methodology. The blood test can detect pregnancy much earlier than a urine test. The sensitivity of the blood pregnancy test is much higher than the home urine pregnancy tests because blood sample is collected to measure the exact amount of the hormone hCG (so even small concentrations of hCG can be detected).

Unfortunately the blood test also can give FALSE POSITIVE PREGNANCY results but only in following cases:

  • if woman take regularly anticonvulsants;
  • if woman take medications for Parkinson’s disease or similar disorders;
  • if woman use regularly tranquilizers;
  • if woman used diuretics during last week.

Women health is pretty complicated and it is more complicated during pregnancy. Better follow all recommendations above to avoid any misinterpretations and useless stresses.

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