6 Errors That Could Make Your Pregnancy Test Invalid

Written by Jessica Holbrook, MSN, RN, CCRN

Published on September 20, 2023

• Home pregnancy tests are typically accurate as long as they are used correctly.
• Failure to follow instructions, a diluted urine sample, and some medical conditions can cause invalid pregnancy tests. 
• Make sure the test kit you use is not damaged or past its expiration date. 
• If you think you got an inaccurate pregnancy test result, you can talk to your healthcare provider and ask for additional testing. 

I vividly remember the first day I suspected I might be pregnant. Around the middle of the day, I just couldn’t wait any longer and decided to take a pregnancy test. I could barely breathe as I took the test and waited for what felt like an eternity for the result. I had always wanted kids but wasn’t sure if I was really ready. 

The test came back negative. However, when I continued to experience pregnancy symptoms, I took another test and found out that I indeed did have a tiny baby growing inside of me. I later found out that my first test was taken too early and was probably too diluted. 

Taking a pregnancy test can be a life-changing event, but there are a lot of reasons your result may not be accurate. 

If you are concerned about your pregnancy test result, you may need to look into one of these six errors that could make your pregnancy test invalid. 

Error 1: Testing Too Early or Too Late

When you’re anxious to find out whether or not you’re pregnant, waiting two or three days to take a pregnancy test can feel impossible. However, testing too early may give you a false negative result. As challenging as it may be, try to wait until the date of your expected period.

Pregnancy tests look for a hormone called hCG in your urine. At the start of pregnancy, hCG levels begin to rise and can double every two to three days in the early part of pregnancy. Pregnancy tests cannot detect hCG until it reaches a certain level.  

The American Pregnancy Association¹1. What are HCG levels?. American Pregnancy Association. https://americanpregnancy.org/getting-pregnant/hcg-levels states that you will get a positive pregnancy test only once your hCG levels have reached at least above 25 mIU/mL. While some tests claim that they will be able to detect pregnancy up to five days before your missed period, waiting until the day of your expected menstrual period is the best way to get accurate pregnancy test results. 

Surprisingly, you can also get an invalid result if you test for pregnancy too late. Most pregnancy tests will give a negative result once the pregnancy hormones get too high. This can happen late in pregnancy or with twin pregnancies.  

Error 2: Incorrect Test Usage

While a home pregnancy test may seem simple to use, there are a few things you have to remember to avoid an invalid pregnancy test result. 

Not Following Instructions

Each pregnancy test should come with a specific set of instructions. These instructions give you information about how to open the package, how long to wait to interpret your test results, and how long a test can sit out before the test kit would be considered an invalid result.

While each test is slightly different, experts at the Mayo Clinic²2. Mayo Foundation for Medical Education and Research. Home pregnancy tests: Can you trust the results?. Mayo Clinic. 2022. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940 state that you will usually have to wait for at least two minutes before interpreting your pregnancy test result. Reading the test too early may result in a false negative. 

In addition, your test kit should have specific instructions about how to interpret your pregnancy test results. Make sure you read the instructions carefully and understand what shape indicates a positive test result, whether it’s two lines, a plus sign, or digital words. 

Over Dilution

You may be surprised to find out that drinking too much water can cause an invalid pregnancy test result. This is because a pregnancy test checks measures the concentration of hCG in urine. 

Imagine having 8oz of coffee with one sugar packet. When you drink the coffee, you’ll be able to taste some sweetness. If you have 24 oz of coffee with the same amount of sugar, you may not notice any sweetness at all. 

Pregnancy tests work the same way. If you have too much water in your urine, the dipstick won’t be able to see the hCG and you will get invalid pregnancy test results. Since most people don’t eat or drink throughout the night, first-morning urine is often more concentrated. Using a morning urine sample can help you avoid an invalid result. 

Error 3: Expired or Damaged Test

Any test taken with an expired or damaged kit should be considered an invalid pregnancy test. If your pregnancy test has expired, been stored at the wrong temperature, has gotten wet, or is cracked, there’s a high chance that it will produce inaccurate results. 

Before you use your test, check the expiration date on the package and make sure your kit has been stored correctly. UNC School of Medicine³3. Pregnancy Test Instructions. UNC School of Medicine. https://www.med.unc.edu/timetoconceive/study-participant-resources/pregnancy-test-instructions/#:~:text=Store%20pregnancy%20tests%20at%20normal%20room%20temperature%2C%20between,direct%20sunlight%2C%20moisture%2C%20heat%2C%20and%20other%20related%20conditions. states that pregnancy tests should be stored at room temperature in a dry environment prior to use. 

Error 4: Medication Interference 

If you’re taking certain medications⁴4. What Medications Can Cause a False Positive Pregnancy Test?. New Health Advisor. https://www.newhealthadvisor.org/what-medications-can-cause-a-false-positive-pregnancy-test.html, you may get a false positive pregnancy test. Medications that help with fertility, some antipsychotic medications, and certain antiseizure medications can cause an invalid pregnancy test. 

If you’re taking any prescription medications and suspect that you may be pregnant, talk to your healthcare professional to find out if you might get false pregnancy test results. 

Error 5: Evaporation Lines

Evaporation lines are a rare cause of an invalid pregnancy test. An evaporation line can look the same as a positive pregnancy test but is caused by urine drying after a negative test. If you follow the instructions and read your test within the 2–5 minute test window given in the instructions and get a negative result, you should discard the test. Tests that are not discarded after a negative result can develop an evaporation line. 

If you think you read the pregnancy test an hour after taking it and it looks like a positive result, you should retest and interpret your test within the instructed timeframe.  

Error 6: Certain Medical Conditions

Some medical conditions such as PCOS and kidney disease can lead to false positives or negatives. This is because these conditions can cause changes in hormone levels, including hCG. Anytime you have a question about whether or not you could be pregnant, you should seek professional medical advice. 

Sadly, a chemical pregnancy or molar pregnancy can also cause misleading results. This may mean that an egg was fertilized and implanted in the uterus but did not grow or develop normally. Chemical pregnancies do not truly produce false positive results, since you truly are in early pregnancy. However, the pregnancy does not last long enough for a baby to have a heartbeat or be seen on an ultrasound. 

Understanding How Pregnancy Tests Work

In order to get accurate results, you should know how a pregnancy test works. 

The Science Behind Pregnancy Tests

Pregnancy tests are designed to detect human chorionic gonadotropin (hCG). HCG is produced by the placenta and helps thicken the uterus during pregnancy. HCG levels start to rise soon after conception and peak at about 10 weeks of pregnancy. 

When pregnancy tests detect enough hCG, they produce a positive result. 

Types of Pregnancy Tests

The most common type of pregnancy test is the home pregnancy test. These pregnancy test kits look for hCG in a urine sample. You can either pee directly on the test or pee into a cup and place the test strip inside the cup. 

Blood tests are more accurate than home tests, but they must be done in a doctor’s office. If you have taken a few home pregnancy tests but doubt the results, you may be able to ask your healthcare provider to give you a blood test. 

Confirming Pregnancy: When to Consult a Doctor

If you take a pregnancy test and get a positive result, you’ll want to call your doctor to schedule your first prenatal appointment for about eight weeks after the start of your last menstrual period. At this appointment, your doctor will typically perform a blood pregnancy test and ask you about your health history. They will talk to you about how to keep yourself and your baby healthy throughout your pregnancy and answer any questions you may have. 

FAQs 

How reliable are digital pregnancy tests compared to traditional ones in terms of avoiding invalid results?

Digital pregnancy tests are not any more or less accurate than traditional ones. No matter what pregnancy test kit you use, follow the instructions carefully to avoid an invalid pregnancy result. 

What should I do if I have contradictory results from multiple home pregnancy tests?

If you take multiple tests, and each pregnancy test shows a different result, you may not have performed the test correctly. If you are certain that you followed the test instructions correctly and are still getting inconsistent results, contact your healthcare provider. 

References

1. What are HCG levels? American Pregnancy Association. https://americanpregnancy.org/getting-pregnant/hcg-levels
2. Mayo Foundation for Medical Education and Research. (2022, December 23). Home pregnancy tests: Can you trust the results? Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/home-pregnancy-tests/art-20047940
3. Pregnancy Test Instructions. UNC School of Medicine. (n.d.). https://www.med.unc.edu/timetoconceive/study-participant-resources/pregnancy-test-instructions/#:~:text=Store%20pregnancy%20tests%20at%20normal%20room%20temperature%2C%20between,direct%20sunlight%2C%20moisture%2C%20heat%2C%20and%20other%20related%20conditions.
4. What Medications Can Cause a False Positive Pregnancy Test? New Health Advisor. (n.d.). https://www.newhealthadvisor.org/what-medications-can-cause-a-false-positive-pregnancy-test.html

The information WonderBaby provides is not intended to be, and does not constitute, medical or other health advice or diagnosis and should not be used as such. Always consult with a qualified medical professional about your specific circumstances.