Here's The Deal With Chugging Water Before A Pregnancy Test

Taking a pregnancy test can be anxiety-inducing, whether you're hoping for a positive or negative. Using an at-home urine pregnancy test seems simple enough, but slight user error could alter results, which is the last thing you want happening. Taking the test too soon could give you a false negative, while letting the stick soak for too long could trigger a false positive. And, what about if you are ready to take the test, but you don't really need to relieve yourself? You might think, "should I drink a bunch of water before taking a pregnancy test?"

If used correctly, at-home pregnancy tests can be up to 99 percent accurate. As the Mayo Clinic noted, pregnancy tests work by detecting the hormone hCG, or human chorionic gonadotropin, in your urine. HCG enters your bloodstream and urine after you become pregnant, and doubles rapidly as your pregnancy progresses. A positive test result shows when the amount of hCG is more than about 50 mIU/ml.

Since these tests are not error-proof, they might be affected by little things. Sarah Winward, BS, doula and founder of Your Downtown Doula, agrees that at-home pregnancy test results can be altered by something like drinking too much water before testing.

Drinking water dilutes your urine, Winward mentions in an interview with Romper, so the more water, the lower the concentration of hCG will be. This is most important with early pregnancy tests, she says, because in the early days your body doesn’t produce very much hCG. Most at-home pregnancy test instructions will recommend you to test first thing in the morning, before drinking anything, while your urine is most concentrated.

Winward also notes that blood pregnancy tests, typically taken by your doctor, are not affected by how much water you’re drinking. It's best to confirm the result of your at-home pregnancy test with one done by your doctor in order to ensure the most accurate results. After all, this is one thing of which you'll want to be sure. So if you're thirsty, go ahead and drink some water, but don't pound back a gallon of Dasani before peeing on the stick. Those pink lines may not be as accurate as you thought.