Why a Pregnancy Test Can Be Wrong

Even a positive test can be wrong sometimes

There are a few reasons why a pregnancy test can be wrong, especially if you are using a home pregnancy test. Consider the various types of testing available as well as conditions that may lead to a false reading.

Types of Pregnancy Tests

There are two basic types of tests for pregnancy and the strategy used depends on the patient's situation.

Blood Tests

Some tests are extremely reliable and you should have no problem getting an accurate reading. A visit to your physician is always a good idea if you think that you may be pregnant and the testing approaches used in doctor's offices are accurate.

Blood tests are not the norm because they are costly and other approaches are almost as reliable. Women undergoing infertility treatments or women with serious health conditions may take blood tests to get early results since it can detect hCG as early as one week after conception.

Urine Tests

More common are urine tests that can be administered by a physician or by the patient using a home pregnancy test. It is important to determine when to take a pregnancy test in order to get the most reliable results. The Mayo Clinic recommends that you wait at least one week after a missed period in order to ensure accuracy, but most over-the-counter tests are accurate on the first day of your missed period.

What Can Go Wrong?

In exploring why a pregnancy test can be wrong, it helps to look at the possible results. Pregnancy tests and false negatives are more common than pregnancy tests false positives. There are a number of reasons for the inaccuracies.

Human Error

Human error is a possible problem when using home kits. You can easily miss a step in the process if you do not read the directions from beginning to end before taking action. It is important to follow the steps in the proper order to ensure a good reading. This includes the right time of day to take the test.

Levels of hCG are higher in the morning, making this the best time to take a pregnancy test. Women who are in the early stages of pregnancy may not have built up enough of this hormone in their systems for it to be detected. Drinking too much water can interfere with a reading because it can dilute the hCG levels in the urine.


Waiting too long after collecting a urine sample can interfere with the reading as well. Many kits can be used by placing the test in the urine stream rather than dipping it into a sample. If you are collecting a sample for a pregnancy test, it is important to make sure that you use it within 15 minutes. On the other hand, you want to make sure that you give the test enough time to work. Some kits require a few minutes to develop an accurate reading. Make sure that you give the test enough time to produce a reliable result and double-check the expiration date on the test's package.

Ectopic Pregnancy

An ectopic pregnancy is very problematic because the egg is fertilized somewhere other than the uterus. This can interfere with the level of hCG in the body, making an accurate reading difficult. Women experiencing sharp pain in the pelvic or abdomen area as well as common pregnancy symptoms should see a doctor immediately.


Some medications can interfere with a pregnancy test, especially drugs for fertility that contain the hCG hormone. Drugs that do not contain the hormone shouldn't interfere with the reading. This includes birth control pills.

Some drugs that do not contain hCG can produce inaccuracies in rare cases. Phenergan (promethazine), a common allergy drug, can interfere with some pregnancy tests. Other drugs can result in a false reading:

  • Some diuretics
  • Anti-convulsants
  • Some tranquilizers

Women taking these medications should consult their physicians if they are trying to become pregnant.

Medical Conditions

Rarely, medical conditions can produce inaccurate results in pregnancy tests. Tumors in the reproductive system and liver problems can interfere in rare cases. Hysterical pregnancy is a psychological condition but it can have serious ramifications on the body, which may include higher levels of hCG. This can lead to an incorrect reading.

Doctor Consultation

Women can trust their intuition when it comes to their bodies. If you have taken a pregnancy test recently and you are uneasy about the results, contact your doctor to explore why a pregnancy test can be wrong in your case.

. .

Why a Pregnancy Test Can Be Wrong