Mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) are two closely related blood test results that indicate how much hemoglobin you have.
Hemoglobin is the molecule within red blood cells that binds to oxygen. It's responsible for the main function of red blood cells — transporting oxygen from your lungs to every cell in your body.
Low MCH or MCHC means that the amount of hemoglobin in your red blood cells is below normal. A low hemoglobin can be caused by not enough iron in your diet.
MCH and MCHC Results
MCH and MCHC are two parts of a blood test called the complete blood count (CBC). As the name suggests, a CBC contains a number of results about all cells in your blood, including red blood cells, white blood cells, and platelets. CBC is a very common test. If your doctor recommends a set of routine blood tests, a CBC will likely be one of them.
MCH represents the average amount of hemoglobin in each of your red blood cells. MCHC represents the average amount of hemoglobin within a specific volume of your red blood cells. It takes into account the size of these cells. Although they are slightly different, a low MCH and a low MCHC both mean that your red blood cells contain less than the normal amount of hemoglobin.
Your body needs iron to make hemoglobin. When the amount of iron in your body is low, hemoglobin production drops, causing a low MCH and MCHC. The total number of red blood cells in your blood — another part of the CBC — will also decrease, resulting in anemia.
Bleeding is the most common cause of iron deficiency, as the body requires extra iron when it increases red blood cell production to compensate for the loss of blood. Inadequate iron in the diet is another cause of iron deficiency.
Less commonly, the body contains an adequate amount of iron but hemoglobin production is still impaired. This may occur with sideroblastic anemia, thalassemia or lead toxicity.
Dietary iron intake can be improved by eating iron-rich foods. Foods high in iron include eggs, red meat, seafood and leafy green vegetables. Other good sources of iron are dried fruits, nuts, beans, peas and iron-fortified foods, such as bread, cereals and pasta.
Absorption of iron from the digestive tract is increased by vitamin C, so foods or drinks rich in vitamin C can improve iron absorption if you consume them with iron-containing foods. High vitamin C foods include citrus fruits, broccoli, kiwi fruit, mangoes, melons, peppers, strawberries and tomatoes.
Oral iron supplements are an option when increasing dietary iron alone is insufficient to improve iron deficiency. When the deficiency is severe, iron injections may be considered. Injections may also be used when iron absorption is impaired.
Dietary iron is absorbed in the first part of your small intestine, so absorption can be reduced by intestinal disorders such as celiac disease or by surgery that removes or bypasses this part of the intestine. As stomach acid converts iron to a form that is more easily absorbed, iron absorption may also be reduced by disorders or medications that decrease stomach acidity, such as antacids.
If you have a low MCH or MCHC, your doctor will likely want to determine the cause. This may require additional blood tests, such as an iron level or a blood smear — a test in which blood cells are viewed with a microscope.
Even if poor dietary intake of iron appears to be the cause, your doctor may recommend investigations to make sure you don't have a source of blood loss, such as an ulcer or tumor in your digestive tract.
Reviewed and revised by Mary D. Daley, M.D.
- Lab Tests Online: Complete Blood Count
- Brigham and Williams Hospital: Iron Absorption
- Merck Manual Professional Version: Iron Deficiency Anemia
- National Institutes of Health: Iron
- Wintrobe's Clinical Hematology, Volume 1; John P. Greer, et al.
- ARUP Consult: Anemia Testing
- Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition; H. Kenneth Walker, et al.