Vitamin B12 (cobalamin) is a water-soluble vitamin that can be stored around 60% in the liver and 30% in the muscles. Due to the good storage options, a deficiency becomes noticeable only after a long time, but relatively suddenly. Food of animal origin being the main sources of vitamin B12, vegans and vegetarians in particular often need an additional contribution. The elderly may also have an increased need, as absorption is often limited or taking certain medications may reduce the amount of vitamin B12 stored in the body.