As we get older, our bodies may have a harder time absorbing vitamin B12. Deficiencies can be caused by medical conditions like atrophic gastritis, which thins the lining of the stomach, pernicious anemia, Crohn's disease, celiac disease, lupus, or other immune system disorders, and by some medications. Learn more about what causes a lack of vitamin B12, what the symptoms are, and how to treat it.
Vegans are more likely to get a B12 deficiency because they don't eat animal products like meat, milk, cheese, and eggs, which are good sources of B12. Low B12 levels or a lack of it can also be caused by things like drinking and smoking a lot or eating poorly for a long time.