What's Wrong With Blue Dye Pregnancy Tests? An OB-GYN Explains

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Taking a pregnancy test is super stressful, and the possibility of false positives, evap lines, and potentially false negatives make it even worse. But in many trying to conceive (TTC) forums and boards, the stress seems to be compounded by pregnancy tests using blue dye. One group I was in even tried to ban people from posting pictures of blue dye tests within the group because they were always seemingly so inaccurate. But what’s wrong with blue dye pregnancy tests?

There is nothing worse than a pregnancy test telling you that you’re pregnant when you're actually not — talk about heartbreak and an emotional letdown. Dr. Sherry Ross, OB-GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, agrees and tells Romper that the blue dye tests are definitely more associated with false positives and are harder to interpret. But why is that? Ross says it’s because the blue dye test works by using an evaporation line that depends on the evaporation of urine, and that line can be colorless, which is often confused as a positive pregnancy test. “The colorless line is more grey or appears as a shadow instead of appearing pink or blue,” she says.

So which tests are the most accurate? Are digitals the way to go, or are pink dye tests easier to decipher and give less false positives? Ross says the pink dye tests are the most accurate and reliable, as well as being easier to interpret than the blue dye tests. As for which tests are the most sensitive and can give you a positive result the soonest, Ross says the digital tests aren’t as sensitive as the dye tests. The most sensitive test you can get would be a blood test at the doctor, she says, where they measure the hCG levels. Otherwise, “Using the First Response Early Result is also a reliable and accurate over-the-counter pink dye test that can be used to detect pregnancy,” she recommends.

So when you’re in Target or shopping on Amazon for pregnancy tests, ideally, it’s probably best to stick to the pink dye tests before doing a blood test at your doctor. Anything to make the situation less stressful for you, since trying to get pregnant and taking that test are stressful enough. Ain’t nobody got time for tricky shadows and false negatives when TTC, so stay clear of the dreaded blue dye tests.