MCH stands for Mean Corpuscular Hemoglobin, and is a calculation of the average amount of hemoglobin contained in each of a person’s red blood cells. Hemoglobin is the substance that carries oxygen from the lungs, to the cells through the bloodstream. Abnormally high or low levels of MCH, as determined by blood testing, can be an indication of a number of problems in the body, ranging from nutrient deficiencies to chronic diseases.

The MCH blood test is done as a component of a blood test called a Complete Blood Count (CBC), which evaluates the composition of the blood, checking hematocrit, white blood cells (WBC) and platelets as well as hemoglobin and red blood cells (RBC). It is usually required to get an overview of one’s general health. MCH is not measured directly, but calculated based on the hemoglobin value (Hgb), which is the total measure of hemoglobin in the blood; and the RBC, which is the number of red blood cells in the blood. To calculate MCH, the Hgb is divided by RCB, yielding an average amount of hemoglobin per red blood cell. Normal levels of MCH are between 26 and 33 picograms (pg) of hemoglobin per RBC.

What Is High MCH and What Can It Mean?

MCH levels over 34 pg are generally considered abnormally high. The most common reason for high MCH is macrocytic anemia, which is a blood disorder in which the body fails to produce enough red blood cells. In macrocytic anemia, red blood cells that are produced are larger than usual, each carrying more hemoglobin than normal-sized cells would. This condition can be caused by deficient levels of vitamin B-12 or folic acid in the body; nutrients found in foods like fish, liver, green leafy vegetables and fortified cereals. These contribute to efficient red blood cell production and may be lacking in your diet, you may not be able to absorb them or there may be other reasons your body cannot process them. Symptoms of macrocytic anemia can include:

  • Unexplained fatigue
  • Heart palpitations
  • Pallor
  • Heart complications

Since this can interfere with heart function, early diagnosis of macrocytic anemia is important. Other possible reasons for a high MCH test include several other forms of anemia, thyroid dysfunction, chemotherapy, certain infections, over use of estrogen-containing medications, some forms of leukemia and hereditary spherocytosis; a condition that causes a shortage of red blood cells.

What Low MCH Test Results Can Indicate?

MCH levels below 26 pg are considered abnormally low. Common causes of Low MCH include blood loss, iron deficiency and microcytic anemia, which is a condition in which red blood cells are abnormally small, carrying less hemoglobin. Other potential causes of a low MCH test include hemoglobinopathy, which is a group of disorders that cause changes in the structure of hemoglobin, and iron-deficiency anemia.

If you have had a CBC done; and, results show MCH levels that are higher or lower than normal, further investigation is warranted. While abnormal results are not necessarily an indication of serious health issues, as noted in the above lists; they can be significant, so it is important to rule them out. Many of the possible causes of abnormal MCH levels require treatment to protect health and well-being, such as anemia or other blood disorders, thyroid disease and nutritional deficiencies.

Your doctor may be able to determine the cause of abnormal MCH results with the help of other components of the CBC, such as MCV results, which measure the average size of red blood cells, or MCHC, which measures hemoglobin concentration. Blood tests to determine your nutritional status may also be done to determine whether nutritional deficiencies are an issue. If your doctor suspects thyroid disease to be the root cause of your abnormal MCH levels, a blood test called a thyroid function panel may be needed to evaluate the health and function of your thyroid gland. Depending on an evaluation of your general health and any symptoms you may be experiencing, your doctor may order a variety of other tests to determine the cause of your high or low MCH results.

A CBC is commonly included in a bloodwork ordered by your doctor during an annual checkup. Also included in this standard test bundling is a comprehensive metabolic panel (CMP), urinalysis, hemoglobin A1c, and lipid panel.

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