It can happen...

Some women never get a good urine hcg level or they have a medical condition that can give a false positive such a certain fertility treatments so blood work is needed. They are usually pretty accurate and work well for almost everyone but you have your rare cases they will not work for and blood work is a safer route to go if that is the case.

most women it does, sometimes you just gotta buy a few and take it at certain times of the day so that you could get the best result. i had to take 2 because my hcg levels came higher at different times of the day.

i myself required a blood test as all the home tests i took came up negative. the blood test was positive. i was 9 1/2 weeks along when i got the blood test and a recent home test had been negative.

Yeah, it's very possible, That's why if you think your pregnant and the unrine test comes back negative you could get the blood test and come out postive. Some women are just made up differently. good luck!