to make a person sick, but an injection with too much riboflavin can make one sick. The kidneys take riboflavin out of the blood. They put it in the urine to get it out of the body. If there is much riboflavin in the urine, the urine becomes bright, yellow. Vitamin pills, or a meal with a lot of liver or egg white turns the urine yellow because these foods put so much riboflavin into the blood.