What are the most common vitamins that people need to take?

Common vitamins that people need to take include vitamin C, thiamine, pantothenic acid, riboflavin, B-12, folic acid and biotin, states WebMD. These are all water-soluble vitamins, and unlike fat-soluble vitamins, they need to be consumed regularly.

Water-soluble vitamins dissolve in water, and the body cannot store them, says WebMD. The body uses the right amount of these vitamins and typically excretes the rest through urine.

Fat-soluble vitamins such as vitamins A, D, E and K dissolve in fat, and the body can store them, note WebMD and MedicineNet. Taking too much of these vitamins can make them accumulate to dangerous levels in the body, causing a condition called hypervitaminosis.