Just Out of Curiosity- Why Is a Pregnancy Test Invalid After 10 Minutes?

No, they're NOT readable after 10 minutes. This causes both windows to fully saturate with urine, and HCG or not, both windows will almost always darken.

One of my girlfriends used to drive me crazy EVERY MONTH reading old tests... PUT THE PEE STICK IN THE GARBAGE AND LEAVE IT ALONE, here are some tampons, you're going to start you're period because you're NOT pregnant, LOL!!

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probably just to cover their butts. I saved a pregnancy test from 12 years ago it still says positive.

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If it turns positive in within the time window, you are cool ;) It will stay positive no prob, did for me anyway. But if it turns positive outside of the time window, it could just be what they call an evaporation line, which could cause a person to have a "false" positive. I will say though that my mom was working with people in crisis pregnancies for a time and they gave someone a test and it read negative in the time window and she left. When they were cleaning up 30 minutes later, it read a faint positive and she was pregnant after all! So you never know! Good luck, hope you get the result you want and if you are pregnant, congrats in advance :D

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there are times when a negative test turns "positive" after about 10 minutes because of evaporation....

My tests from my boys are still positive after 12 and 10 years...I kept them in those bio-hazard bags that my doctor gave me.

Good luck!!!

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My tests from my 2 are still positive and they have been in a drawer for almost 6 and 3 years.

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Okay I am both amused and a little grossed out at people who actually saved their pregnancy tests! ;)

Anyway, the others basically said it...the test is essentially a fancy litmus paper and it could change "results" after a certain period of time from the air, the amount of liquid, various other things. Although it probably won't, you can't be sure, so they don't want to get sued!

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I believe it is because the result display fades and therefore may be misread.

this is no scientific answer, just based on my own experience, but you can get a false positive if you read it too late. After a while, some tests will just revert to all of the lines. I had this experience with a test I took at night and it was negative but in the morning it was positive but I was not pregnant.

I thought it was because evaporation lines can show up by then and confuse people

A friend of mine took a pg test (she and her husband were trying) and it was negative, so she threw it in the trash. For whatever reason, she decided to go back and check it again after about 15 mins. It was positive. She was definitely pregnant.