If you’ve had unprotected sex recently, then you’re probably thinking about taking a pregnancy test. And you’ve probably got a few questions about them. Like ‘How long do I need to wait before taking one?’ and ‘How do I make sure I’m getting the most accurate results possible?’ To answer those questions (and more), we spoke to Dr. Anna Whelan, an OB-GYN and maternal-fetal medicine fellow at the Women and Infants Hospital of Rhode Island.
How soon after unprotected sex can I test for pregnancy?
Rule of thumb: For the most accurate results, wait a minimum of two weeks after having unprotected sex to take a pregnancy test, said Dr. Whelan. That’s true for both at-home and blood tests. That’s because your body needs time to build up hCG, the hormone that’s produced during pregnancy. And the one that’s analyzed in pregnancy tests. If you take a pregnancy test too early, there’s a chance you could get a false negative.
How accurate are pregnancy tests?
To test for pregnancy, you have two options. And they’re both precise.
An at-home test is 97% to 99% accurate when used correctly (more on that below). A blood test, performed at a doctor’s office or lab, is around 99% accurate.
If you get a positive result at home, call your doctor. Your provider can help you confirm the pregnancy. But it’s rare to get a false positive result. So even if the lines on the test are faint, it still means you’re pregnant.
A blood test, ordered by a doctor, is your other option. Note: A blood test can detect lower levels of hCG than an at-home test can, but it can take longer to get results due to lab processing, said Dr. Whelan. After getting a positive result at home, it’s common for a doctor, at your first appointment, to order a blood test to confirm the results. Your doctor might also order a blood test if you’re experiencing bleeding or abdominal pain, which can be symptoms of a potential miscarriage.
How can I make sure the pregnancy test results are as accurate as possible?
Experts recommend you:
Take the test in the morning: That’s when hCG is most concentrated in your urine, said Dr. Whelan.
Read your results ASAP: Follow the instructions on the package closely. Waiting to check the results after the recommended amount of time can lead to a false positive. (For example, a First Response Early Result Pregnancy Test will show results in three minutes).
Avoid drinking too much water or other liquids beforehand: Because diluting your urine could interfere with the test’s ability to detect your hCG levels properly.
Store the test correctly: Store the test between 36 and 86 degrees Fahrenheit. That'll help slow down the expiration process. Speaking of which...
Double check the expiration date: Because the antibody coating on a pregnancy test can begin to evaporate and lose its effectiveness over time. At-home tests typically last about one to three years after manufacturing.
Of course you’ll want to know as soon as you can if you’re pregnant. But to get the most accurate results, it’s best to wait at least two weeks after having unprotected sex before taking a pregnancy test. And if you’re confused or concerned about your test results, speak with your medical provider.
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