How important is B12 in older adults?

There are many reasons a person might be deficient in B12. One may have a vitamin B12 deficiency due to being vegan, vegetarian or having an autoimmune disease, including type 1 diabetes, Crohn's disease, HIV. Some medicines such as gastric acid inhibitors, anti seizure medicines, and metformin can interfere with B12 absorption as well. Poor diet and chronic inflammation of the stomach lining is also a common cause. As we age stomach acid is reduced and can cause malabsorption.