Hi. I use a Ketostix about once a week to make sure I am still in Ketosis.... I take a Multi-vitamin as well. Yes, it does change the color of your urine a bright yellow. Not a problem..... I use the Ketostix as soon as I get up. My first potty trip of the day. I don't take my vitamins until later, so I always get the same reading. Vitamins are important, so I wouldn't give them up. Bye. Suzanne.