Anemia is a decreased number of circulating red blood cells and is a common medical condition faced in clinical practice. Anemia is caused by loss of red blood cells, destruction of red blood cells, decreased production of red blood cells, or a combination of these processes. Through a clinical history, physical examination, and laboratory evaluation the provider must identify the process by which the patient is anemic. Often the cause of anemia is straightforward; however, the cause can be challenging, requiring a thorough knowledge of both hematology and general medicine.