If you’re wondering if you’re unexpectedly pregnant, it can feel like you’re waiting forever to know for sure. So, you may stop at the store to pick up a pregnancy test but ask yourself if you can trust the results of a home pregnancy test.
Read on to learn more about how home pregnancy tests work and ways to increase the likelihood of getting accurate test results.
How Home Pregnancy Tests Work
When you become pregnant, the fertilized egg travels through the fallopian tube and implants into the lining of the uterus. This is called implantation. Once implantation occurs, the placenta produces a pregnancy hormone, human chorionic gonadotropin (hCG).
Home pregnancy tests work by detecting the presence of hCG in your urine. If hCG is found, the test will read positive. If the test does not recognize hCG, the pregnancy test result will be negative.
How Soon Can You Take a Home Pregnancy Test?
Although there are early pregnancy tests that market the ability to provide a positive test result 4-5 days before you miss your period, your body must have enough time to produce detectable amounts of the hCG hormone to avoid getting a false negative test result.
If you are indeed pregnant and take a test five days before your period is due, the test will only be able to detect it up to 76% of the time – and that’s under perfect laboratory conditions. For that reason, it’s advised to wait until you have missed your period before taking a pregnancy test.
What Can Cause a False Negative Pregnancy Test Result?
A false negative pregnancy test happens when the result reads negative when you are pregnant. There are several reasons you can get a false negative test result, and they include:
1. Testing too soon – before hCG can be detected in your urine
The most common reason for a false negative pregnancy test is taking the test too early when hCG levels aren’t high enough to be detected in your urine yet. There are a few reasons this can happen. First, you may have miscalculated when your next period was due, so recheck the calendar for accuracy.
It’s also possible that something caused a delay in ovulation, which would also cause conception and implantation to occur later than expected in your menstrual cycle. When this happens, you won’t get an accurate test result until later in your cycle. You can try waiting a few days and testing again.
2. Your urine is diluted
You can still get a false negative test result even if you wait until you miss your period to test. This can happen if you drink a lot of fluid before taking a pregnancy test, making your urine too diluted to pick up on hCG levels accurately.
3. Testing errors
You can also get a false negative test result if you make a mistake on the pregnancy test directions. They are all a little bit different, so even though you are anxious to get answers, take the time to read the insert thoroughly before testing.
Also, set a timer and read the result at the time listed in the directions. If you estimate, you may accidentally read a negative test too soon.
4. A faulty pregnancy test
It’s possible to get a false negative result if the pregnancy test isn’t working correctly. This can happen if the test is defective or if it’s expired. Always check the expiration date before taking a test for the most accurate results. Also, store pregnancy tests in a dry place because being stored in a hot, damp bathroom can cause them to fail.
5. Medical conditions
Certain medical conditions, such as ectopic pregnancy, can also cause a false negative pregnancy test. An ectopic pregnancy occurs when the fertilized egg implants outside the uterus, usually in a fallopian tube. It’s a medical emergency that requires immediate intervention.
6. Very high levels of hCG
The least common reason for a false negative pregnancy test result is that your pregnancy hormones are extremely high, creating a “hook effect.”
In a typical pregnancy, hCG levels don’t go higher than 300,000mIU/mL. The hook effect occurs when hCG levels rise above 500,000IU/mL. The high level of hCG overwhelms the testing strip causing the antibodies not to bind, thereby giving a false negative test result.
If you have symptoms of pregnancy but continue to test negative, seek care from a health professional to rule out medical conditions that can cause a hook effect.
In addition to false negative test results, it’s also possible to get false positive results.
What Can Cause a False Positive Pregnancy Test Result?
A false positive pregnancy test is a positive result even though you’re not pregnant. False positives are not as common as false negative results but can occur for several reasons, including:
1. Chemical pregnancy
A chemical pregnancy happens when the fertilized egg implants in the uterus but doesn’t develop into an embryo. This may cause you to produce hCG, leading to a positive pregnancy test.
2. Misreading evaporation lines
Sometimes a faint evaporation line can appear on the pregnancy test, which can be mistaken for a positive result. Ensure that you aren’t reading the test beyond the time allotted in the instructions to minimize this.
3. A recent pregnancy
If you’ve recently given birth, had a miscarriage, or had an abortion, it can take several weeks for hormone levels to return to normal. That means it’s possible to have hCG in your system still if you test during that time, giving you a false positive result.
4. Certain medical conditions or medications
Ovarian cysts and other types of medical conditions can produce hCG. Fertility drugs and other medicines can contain hCG. Either one of these scenarios can create a false positive test result.
Next, we will recap how to get the most accurate pregnancy test results.
How To Get an Accurate Pregnancy Test Result
The following tips will help you get the most accurate test results:
- Wait until you miss your period to take a home pregnancy test.
- Test when your urine is most concentrated.
- Follow the directions exactly as written.
- Store pregnancy test kits in a cool, dry place.
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Danielsson, K. (2023, January 2). Pros and cons of doing an early pregnancy test. Verywell Family. Retrieved from https://www.verywellfamily.com/using-an-early-pregnancy-test-2371541
Human chorionic gonadotropin: Hormone, purpose & levels. Cleveland Clinic. (2022, March 11). Retrieved from https://my.clevelandclinic.org/health/articles/22489-human-chorionic-gonadotropin
Mayo Foundation for Medical Education and Research. (2022, March 12). Ectopic pregnancy. Mayo Clinic. Retrieved from https://www.mayoclinic.org/diseases-conditions/ectopic-pregnancy/symptoms-causes/syc-20372088