Has any of you had to do a 24hs pee test?

Bárbara • I'm 28, and I have a beautiful baby girl born on May 30th, 2017 ^^ I also have a dog named Oliver and I love him lots!
I don't know the technical name lol but they told me I need to pee on a container for 24hs and then take it to the lab, they asked for this because I've been having some high blood pressure. Has any of you had to do this? Do you know what it is that they are searching for? I'm nervous! Thanks ^^