How Accurate Is My Pregnancy Test?
Spoiler alert: you can probably trust the result
Regardless of how you feel about a positive pregnancy test, it’s helpful to know whether you can really trust the result or not. It might be hard to believe that a test you bought while getting groceries is actually reliable. Is peeing on a plastic stick actually a good way to know whether you’re pregnant?
It turns out that the answer to that question is, “yes!” Here’s why, and some alternatives should you need them.
How pregnancy tests work
Pregnancy tests detect a pregnancy hormone in your body called human chorionic gonadotropin, or hCG for short. hCG is a hormone made by the placenta. Unless you’re currently pregnant, you’ll only have very trace amounts of hCG in your blood or urine.
For your information
Some medications, including fertility treatments, contain hCG. Medications are one of the only reasons you’d have higher levels of hCG and not be pregnant
During pregnancy, hCG levels increase very quickly. Because of this rapid increase and the fact that there’s very little hCG present in non-pregnant bodies, false positives are rare. False negatives are much more common.
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Urine pregnancy tests
At-home urine pregnancy tests are the most common method for diagnosing pregnancy. These tests are affordable and private. Plus, it takes only a few minutes to get results! When used correctly, urine pregnancy tests are 97-99% accurate.
At-home pregnancy tests available in drugstores are getting much better at detecting pregnancy earlier. Some now give you results as early as the first day of a missed period! Almost all of these tests detect pregnancy 1 week after a missed period, or about 5 weeks of pregnancy.
You can take a urine test to confirm your pregnancy at home or at your provider’s office. These tests are widely available in most grocery stores and drugstores. You can also order them online.
You don’t need to buy the most expensive test. Cost and accuracy are not related. It’s more important that you feel comfortable reading the test results. If the two lines type of result will make you stressed, try one that just says “pregnant” or “not pregnant.” If you’re comfortable with the two lines, go for that.
Confirming pregnancy with blood tests
The other way to measure hCG is through a blood test. Blood tests are just as accurate as urine tests (about 99% accurate), but they may detect pregnancy a few days earlier. These tests are typically only done in a medical setting, such as a clinic or office.
For your information
If you miscarry, a blood test will show a decrease in your hCG levels. Unlike urine tests, which are a simple yes/no, some blood tests can measure precise amounts of hCG.
Because of the accuracy of urine tests, most providers don’t consider blood tests necessary to confirm a pregnancy. However, if you take a urine test twice and get different results, a blood test is a good idea to confirm results. Blood tests are also helpful in certain clinical situations, like trying to figure out if you are having a miscarriage.
When to test
The home test kit you choose will tell you the earliest it can detect pregnancy (typically between the first day of a missed period up to one week after). If you have an irregular cycle or are uncertain of your last menstruation date, wait at least 14 days from your most recent sexual act or from when you suspect you got pregnant before performing a pregnancy test.
If you’re getting a pregnancy confirmation at a clinic, use the same timeframes.
Causes of inaccurate test results
There are a few reasons your at-home test might be incorrect. Perhaps unluckily, most of these reasons are due to human errors. False positives are extremely rare due to the levels of hCG needed to trigger a positive test result.
If you get a negative result, you’re probably not pregnant. But you may still be pregnant if:
- The test is past its expiration date.
- You took the test the wrong way.
- You tested too soon.
- Your pee is too diluted because you drank a lot of fluids right before the test.
- You’re taking certain medications, such as diuretics or antihistamines.
For your information
Though it may be tempting to order pregnancy tests in bulk, check the expiration dates before buying! Expired tests are less accurate.
If you get a negative result but still think you’re pregnant, try retesting within about a week to double-check. Some home pregnancy tests suggest doing this no matter what your first results are. Testing your urine first thing in the morning may also boost the accuracy.
What next?
If you get a positive result, the most important step is finding a provider you can trust. They can give advice for ways to take care of yourself and walk you through your options if you’re unsure about keeping the pregnancy.
Not sure where to go? Get virtual pregnancy care with one of our midwives. We can help with everything from finding providers to options counseling and more.
An earlier version of this article was written by Kate Wortham, LM, CPM.