What Are the Effects of Vitamin B12 Deficiency?

Vitamin B12 is required for proper red blood cell formation, nerve function and DNA synthesis. It is naturally present in fish, meat, eggs and dairy products, as well as some fortified breakfast cereals and nutritional yeast products.

Strict vegans who avoid animal products can develop a deficiency of B12 over time if they don’t take a supplement. But two-thirds of cases occur in the elderly, who are susceptible because they may not absorb adequate amounts of B12 from foods but who are not routinely tested, Hensrud said.

Consequences of B12 deficiency can cause a range of symptoms that include fatigue, weakness, constipation, loss of appetite and weight loss. Other symptoms include difficulty maintaining balance, depression, confusion, dementia, poor memory and soreness in the mouth or tongue.

B12 deficiency may also result in a form of anemia called megaloblastic anemia, which can also result from a deficiency of folic acid, another B vitamin. If anemia is detected on blood tests, levels of both vitamins should be checked.

Neurological symptoms can, however, occur in the absence of anemia. Early treatment is critical to avoid potentially irreversible damage.

Older adults are susceptible to B12 deficiency because they may have decreased secretion of hydrochloric acid in the stomach, which makes it difficult to absorb B12.

Also vulnerable to B12 deficiency are those with gastrointestinal disorders like celiac disease or Crohn’s disease; those who have had weight loss or other gastrointestinal surgery; and those who use certain acid reflux drugs or the diabetes drug metformin. Individuals with pernicious anemia, which affects up to 2 percent of older adults, are also susceptible.