An increase or decrease in MCH is usually accompanied by a change in MCV in the same direction. An increase above the norm indicates macrocytic hyperchromic anemia, i.e. anemia with red blood cells that are too large and too heavily stained. The most common cause of such anemia is a deficiency in folic acid or vitamin B12 (cobalamin).
More rarely, elevated levels of MCH and MCV can indicate malignant diseases of the blood, such as a plasmacytoma. A lowered MCH level in combination with a lowered MCV indicates microcytic hypochromic anemia, i.e. anemia with too small and too weakly stained red blood cells. The cause is iron deficiency anemia.
Iron deficiency is generally the most common cause of anemia, women are more frequently affected. Rarely, thalassemia, a disease affecting the hemoglobin molecule, can be the cause of anemia with decreased MCH and MCV.Inflammation and tumors can also lead to microcytic anemia (MCH and MCV decreased), but more often these are associated with normal MCH and MCV. However, even if MCH and MCV are within the normal range, this can be taken as an indication.
There are forms of anemia in which neither of the two values is abnormal, and this is known as normocytic anemia, i.e. anemia in which the cells look normal. Such a form of anemia can occur, for example, in an anemia triggered by the kidney (renal anemia). A hormone (EPO) is produced in the kidney, which stimulates the reproduction of red blood cells in the bone marrow. If the kidney is restricted in its function, too little of this hormone (EPO) is released and this leads to normocytic anemia. Normocytic anemia can also occur if red blood cells are eliminated prematurely (hemolytic anemia) or if red blood cells are lost during bleeding (internal or external).