What does it mean when you have abnormally small red blood cells?

Microcytosis causes. Abnormally small red cells may be due to a number of reasons that include acquired or hereditary disorders of the main protein found in red cells-called hemoglobin. The most common causes inlclude iron deficiency, anemia of chronic disease and rarer forms such as sideroblastic anemias and thallasemias. If you or someone you know has this result in CBC, plase consult your MD ,a hematologist now.
Low iron thalassemia. Small red blood cells, as determined by the MCV is most common in either iron deficiency or thalassemia. Rarer causes include sideroblastic anemia, lead toxicity, chronic inflammatory anemia, or renal/hepatic malignancies.