Vitamin B12 insufficiency or deficiency is a common problem among adults and children alike. It means that there are inadequate levels of the vitamin B12 in the body. But because its symptoms can overlap with other deficiencies or diseases, unfortunately, it can get overlooked or misdiagnosed.
According to WebMD, while B12 is stored in the liver for up to five years, you can eventually become deficient if your diet doesn't help maintain the levels.