Anemia is the most frequent consultation in Hematology. Its causes are multiple and a careful clinical history can guide towards the disease or disorder that causes it. The definition and assessment of the degree of anemia is established by a blood count parameter called hemoglobin. It is common for the patient to go to the hematologist consulting for anemia according to the number of red blood cells or red blood cells that appears in her analysis. Clinical hematologists assess and classify anemia according to the hemoglobin level and the size of the red blood cell, not by the number of red blood cells. A hemogram parameter called mean corpuscular volume (MCV) that measures the size of the red blood cell, guides us on its possible causes.

In general, the study of the cause of anemia begins with the request for an analysis that includes various values such as the blood count, the number of reticulocytes (young red blood cells), the determination of serum iron, ferritin, the saturation index of transferrin and vitamin B12, among other requested values. The microscopic examination of the blood is fundamental, since it also helps to establish its cause by the morphological appearance of the red blood cells and the rest of the blood cells.

In clinical practice, the most frequent causes of anemia are of digestive or gynecological origin, either due to abnormal bleeding originating in some anatomical location of the digestive tract or due to excessive menstrual losses (iron deficiency anemia). Consequently, it is common to request digestive endoscopic examinations to determine the possible source of blood loss in case of suspicion that the anemia has a digestive origin. This situation is frequent when the patient is a man or a woman with menopause who consults for anemia. In this condition, it is always necessary to find out the cause before starting iron treatment.

However, there are many other more complex causes of anemia that require other types of examinations such as a bone marrow exam, if it is assumed that the problem is caused by difficulty in the production of red blood cells. The difficulty in forming red blood cells can be due to a deficiency (iron, vitamin B12) or it can be the result of a primary disease of the bone marrow, either due to alteration of the hematopoietic stem cells or due to abnormal occupation of the marrow space by some neoplastic proliferation originating in the bone marrow or in some other tissue or organ that has colonized the bone marrow. On the other hand, chronic inflammatory diseases such as rheumatoid arthritis, polymyalgia rheumatica and various intestinal diseases are frequently associated with a variable degree of anemia, which can be both due to blood loss in the case of intestinal diseases, as well as due to blockage or impossibility utilization of iron from medullary deposits due to the chronic inflammatory state (inflammatory anemia).

Anemia, therefore, is not a disease per se, but rather a haematological alteration that can be caused by numerous diseases of various origins, whether they are haematological or of other causes: digestive, gynecological, deficiency, inflammatory or tumoral. In short, clinical hematologists are the most qualified specialists to quickly and accurately diagnose the cause of anemia and to be able to offer the best treatment for its cure.