The human body needs vitamin B12 to produce red blood cells, DNA, and nerves, and to carry out other functions. On average, an adult should get 2.4 micrograms of vitamin B12 a day. B12, just like most vitamins can’t be made by the body. Instead, it must be provided to the body through diet or B12 deficiency supplements.

And this is where the problem lies: Most people don’t consume enough vitamin B12 to meet their needs, while others cannot absorb enough, no matter how much they take in, even through capsules and tablets. This makes vitamin B12 deficiency relatively common, especially among older people.