What does B12 deficiency cause?

Anemia. The most common complication of B12 deficiency is anemia. Pernicious anemia, which is an autoimmune process that can cause profound B12 deficiency, is associated also with neurologic symptoms such as weakness/numbness/tingling, memory problems, personality changes. The tongue can become shiny and sore. Symptoms respond to vitamin B12 supplementation, frequently injections if pernicious anemia.
B12. Makes red blood cells to carry oxygen in body. Lowb12 can lead to anemia, your body does not have enough red blood cells. This can make you weak ; tired. Low B12 can cause damage to your nerves and can impact memory and thinking.