Riboflavin is one of the B vitamins (vitamin B2). The B and C vitamins are the vitamins that dissolve in water. A healthy person's gut can easily take riboflavin from food and pass it on to the blood for the body to use. The body needs the B vitamins to get energy from food. Without riboflavin and the other B vitamins people's bodies cannot use fats, carbohydrates, and proteins.

These foods have a lot of riboflavin. We say that they are rich in riboflavin or good sources of riboflavin:

Light can break down riboflavin molecules into other molecules that the body cannot use.

If anyone eats too much riboflavin, the gut does not take up enough to make a person sick, but an injection with too much riboflavin can make one sick. The kidneys pass riboflavin out in the urine, so when there is too much riboflavin in the body, the part that one does not want will not stay in the blood for long. If there is much riboflavin in the urine, the urine becomes bright, fluorescent yellow. Vitamin pills, or a meal with a lot of liver or egg white turns the urine yellow because such foods put so much riboflavin into the blood.

To make Vitamin B2 for vitamin pills or to add to foods, industrial companies grow special yeasts, other fungi, or bacteria that make a lot of riboflavin.

Riboflavin is yellow or orange-yellow, so it can be useful as a food coloring. People get some very bad kinds of sickness (deficiency diseases) when their food has too little riboflavin. Adding extra riboflavin can stop people from getting such sicknesses. To prevent riboflavin deficiency, people may add riboflavin to baby foods, breakfast cereals, pasta, sauces, fruit drinks, and foods such as cheese that are made from milk (dairy products). People call it fortification with riboflavin when they add riboflavin to food. A lot of the riboflavin that people make, they use in vitamin pills.