What is the most common cause of anemia in older adults?

Anemia is not a diagnosis but manifestation of reasons causing it and acute and chronic blood loss is the primary form caused by a variety of reasons. It should be investigated by an MD

There are many potential causes, but poor dietary intake of iron containing foods is the more common one. In the absence of some item in the patients history or exam, a common first approach to mild anemia is iron supplementation for a month followed by repeat testing.