macrocytic anemia

pathology

Also known as: macrocytic hyperchromic anemia

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 30, 2026

Quick Summary

Macrocytic anemia is a blood disorder characterized by the presence of abnormally large red blood cells, known as macrocytes, in the blood. This condition arises from impaired red blood cell production, often due to a deficiency in vitamin B12 or folic acid.12

When there's a lack of these essential vitamins, the bone marrow's ability to produce healthy red blood cells is significantly hindered. While cells proliferate, they don't mature correctly, leading to ineffective erythropoiesis. This results in fewer young red blood cells and a reduction in other blood cell types as well. The mature red cells that are produced are larger than normal, causing macrocytic anemia. This impaired production is also associated with accelerated destruction of red blood cells, contributing to the characteristics of hemolytic anemia.2

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

blood disease
Anemia
Macrocytic anemia, in which the average size of circulating red cells is larger than normal, results from impaired production of red cells—e.g., when vitamin B₁₂ or folic acid is lacking. In other circumstances—for example, when there is a deficiency of iron—the circulating red cells are…
Read More
Macrocytic anemia, in which the average size of circulating red cells is larger than normal, results from impaired production of red cells—e.g., when vitamin B₁₂ or folic acid is lacking. In other circumstances—for example, when there is a deficiency of iron—the circulating red cells are…
Read More

anemia
…into the following types: (1) macrocytic anemia, characterized by larger-than-normal red cells (e.g., pernicious anemia), (2) normocytic anemia, characterized by a decrease in the number of red cells, which are otherwise relatively normal (e.g., anemia caused by sudden blood loss, as in a bleeding peptic ulcer, most cases of hemophilia,…
Read More
…into the following types: (1) macrocytic anemia, characterized by larger-than-normal red cells (e.g., pernicious anemia), (2) normocytic anemia, characterized by a decrease in the number of red cells, which are otherwise relatively normal (e.g., anemia caused by sudden blood loss, as in a bleeding peptic ulcer, most cases of hemophilia,…
Read More