A false positive pregnancy test is rare, but it can happen.
What is it exactly? A false positive pregnancy test is when your home pregnancy test says you’re pregnant, but in fact you’re not.
You might have a positive pregnancy test result and then your period arrives a few days later.
Sometimes, following a positive urine test, a blood test shows there is no pregnancy hormone in your blood.
False Positive Pregnancy Test
Whether you’re trying to conceive or hoping you are not pregnant, a false positive pregnancy test can be frustrating.
This article looks at what a false positive pregnancy test is and what causes it.
Today’s home pregnancy tests (HPTs) claim an accuracy rate of between 97% and 99%, if performed correctly.
This means 1-3% of tests are inaccurate. They could be:
- False negative
- False positive
A false negative pregnancy test is more likely to occur than a false positive one.
This happens when you’ve tested too early and there isn’t enough pregnancy hormone to be detected.
A false positive occurs when you have a positive result but you’re not actually pregnant.
An inconclusive test shows nothing in the results window.
Can you get a false positive pregnancy test?
Home pregnancy tests are the most common way to check whether or not you are pregnant.
The test works by detecting a particular hormone in your urine. This is human chorionic gonadotropin (hCG).
Your body produces hCG when a fertilised egg implants in your uterus.
The cells that eventually become the placenta secrete hCG.
The more sensitive tests can detect lower levels of hCG than other tests can.
If you have a positive HPT and then your period begins a few days later, it’s unlikely the test was inaccurate.
Although non-pregnant women have a small amount of hCG present in their system, the amount is too small to be detected by an HPT.
So it begs the question: how do you get a positive result if you’re not pregnant?
What causes a false positive pregnancy test?
There are several reasons why you might get a false positive pregnancy test. Below are 7 of the most likely reasons your test might show an inaccurate result.
#1: Incorrect use of the test
The accuracy of an HPT depends on following the instructions to the letter.
These factors can affect the accuracy of your HPT:
- The collection cup isn’t sterile. Even detergent residue can skew the results.
- Leaving the test for too long before looking at it. Always check the results in the timeframe given in the test instructions. After this time, you might see what is known as an evaporation line. Read more in Faint Line On A Pregnancy Test – What Does This Mean?.
- You’ve left the test somewhere where it has been affected by heat or moisture, both of which can affect the test’s accuracy.
- Not following the instructions. They are in the box to make sure you get the most accurate result, so make sure you follow them! They include: when to do the test; what to do before collecting your urine; and how long to wait for the result.
#2: Faulty test
Every test kit has an expiration date, which means you shouldn’t use it after this date has passed.
It’s common to buy multiple test packs, only use one or two tests, then leave the rest sitting in the bathroom cupboard.
By the time you need to use another, it’s likely the test has passed its expiration date.
It’s best to buy a test as you need it, rather than use one that’s been sitting in your bathroom cupboard for ages.
There are certain medications that might result in a false positive pregnancy test.
What medications can cause a false positive pregnancy test?
Most medications cannot create a false positive pregnancy test. However, medications that contain hCG can cause a false positive pregnancy test result.
These medications are often used in some fertility drugs. Commonly prescribed anti-anxiety drugs, such as Valium or Xanax, can also cause a false positive result.
Other medications that can affect the accuracy of pregnancy tests include:
- Medication for Parkinson’s disease.
#4: Recent pregnancy
If you recently gave birth, experienced a miscarriage, or had a pregnancy termination, it’s possible for hCG to be present in your system.
That’s because hCG doesn’t disappear from your body immediately after a pregnancy has ended.
Instead, the level decreases and returns to zero gradually. It can take days or even weeks, depending how far the pregnancy had progressed.
Home pregnancy tests are very sensitive and can pick up low levels of hCG.
Doing a pregnancy test at home in the days or weeks after giving birth, or after a miscarriage or termination can give you a false positive result.
#5: Chemical pregnancy
It’s possible to have a positive pregnancy test result when you’re technically not pregnant.
This is known as a chemical pregnancy and happens when a fertilised egg can’t implant properly or grow very early on.
In this case, a woman’s period would begin at about the usual time.
Until the advent of early pregnancy tests, a chemical pregnancy wouldn’t have been detected.
Today’s pregnancy tests are so sensitive, however, they can pick up even this level of hCG.
This is why it’s recommended to wait for a week after your period is due before taking the test.
Read more about this in Chemical Pregnancy – Symptoms Of A Chemical Pregnancy.
#6: Ectopic pregnancy
Very rarely, a fertilised egg will implant outside the uterus, causing an ectopic pregnancy.
Usually the egg gets stuck in a fallopian tube and will produce hCG, even though it’s not a viable pregnancy.
You can read more about the symptoms and treatment of Ectopic Pregnancy.
#7: Medical conditions
There are some medical conditions that can lead to you seeing a false positive pregnancy test result.
The most likely reason is blood or protein in your urine. Blood can be the result of having a urinary tract infection.
The presence of protein is more serious; this indicates kidney problems.
Other and much rarer conditions that can cause false positive pregnancy test results are:
- Kidney disease, which causes blood or white blood cells in the urine
- Ovarian tumours, which produce hCG
- Ovarian cysts
- Ovarian cancer
- Problems with the pituitary gland.
A false positive pregnancy test is a rare occurrence, but if you’re trying to conceive it can be devastating.
If you have any concerns about a test result or your ability to conceive, seek the support and guidance of a trusted health professional.