Microcytic anemia

Microcytic anemia is anemia in which red blood cells are smaller than normal, typically indicated by a low mean corpuscular volume. It commonly results from impaired hemoglobin production.

Mean corpuscular volume: Mean corpuscular volume is the average volume of red blood cells, reported in a complete blood count. A low value is the standard laboratory measure used to identify microcytosis.
Complete blood count: A complete blood count measures blood-cell numbers and characteristics, including hemoglobin and red-cell indices. It provides the measurements that establish anemia and reveal small red cells.
Peripheral blood smear: A peripheral blood smear is a microscopic examination of blood cells spread on a glass slide. Cell shape and appearance can add clues beyond the mean corpuscular volume.
Normocytic anemia: Normocytic anemia is anemia in which red blood cells have an average size within the usual reference range. It contrasts with microcytic anemia by having a normal rather than reduced mean corpuscular volume.
Iron-deficiency anemia: Iron-deficiency anemia is anemia caused by insufficient iron for normal hemoglobin production. Iron shortage is a common cause of microcytosis and limits hemoglobin synthesis.
Hemoglobin: Hemoglobin is the iron-containing protein in red blood cells that transports oxygen. Reduced hemoglobin defines anemia, while impaired production often underlies microcytosis.
Iron studies: Iron studies are blood tests that assess iron stores, transport, and availability. They help identify iron deficiency and separate it from other causes of microcytosis.
Macrocytic anemia: Macrocytic anemia is anemia in which red blood cells are larger than normal on average. It lies at the opposite end of red-cell size classification.
Thalassemia: Thalassemia is an inherited disorder in which reduced production of globin chains disrupts hemoglobin formation. Globin-chain imbalance produces small red cells, often with a different pattern from iron deficiency.
Red blood cell distribution width: Red blood cell distribution width measures variation in red-cell size in a blood sample. Its pattern can help distinguish iron deficiency from some inherited causes of microcytosis.

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Iron deficiencyNarrower topic: Iron deficiency is a common cause, but microcytosis also has other explanations.