Anemia: Definition, Types, and Causes

Anemia is a condition in which the oxygen-carrying capacity of blood is reduced due to low hemoglobin levels

or decreased red blood cells, with WHO defining anemia as hemoglobin <13 g/dL in men

and <12 g/dL in women. It is not a disease but a clinical sign of underlying pathology

and presents as acute symptoms such as tachycardia and dyspnea or chronic symptoms including

fatigue, weakness, and pallor. Pathophysiologically, anemia occurs through

decreased red blood cell production, increased red blood cell destruction, or blood loss,

with the body compensating by increasing heart and respiratory rates. Anemia is classified

by red blood cell size into microcytic anemia (commonly iron deficiency), normocytic anemia