The mean corpuscular hemoglobin (hgb) is a laboratory study that is performed to evaluate the red blood cells. It is one of the many results reported as part of the complete blood count, which is a commonly done lab test. Evaluating the amount of hemoglobin present in red blood cells is important because hemoglobin is responsible for carrying oxygen throughout the body. Low mean corpuscular hemoglobin levels reflect a condition called microcytosis, whereas high levels correlate to macrocytosis.
Mean corpuscular hgb, also known as the mean cellular hgb, is often abbreviated as MCH. It is a measure of the average hemoglobin concentration present in a red blood cell. MCH is reported as part of a complete blood count (CBC), which is a study that measures the number of white blood cells, red blood cells, and platelets present in the blood. The CBC gives a significant amount of information regarding the red blood cells, including the concentration of hemoglobin in the blood, the MCH, the mean corpuscular hemoglobin concentration (MCHC), the mean corpuscular volume (MCV), and red cell distribution width (RDW).
In order to understand why measuring the mean corpuscular hgb is important, it helps to understand the role that hemoglobin plays in the physiology of the body. Hemoglobin is a protein located within red blood cells, and it is responsible for carrying oxygen. Typically this protein picks up oxygen molecules in the lungs, carries the oxygen to distant parts of the body, and drops it off for these cells to use as part of their metabolic processes. Without enough hemoglobin circulating in the blood, insufficient amounts of oxygen will be distributed throughout the body.
The mean corpuscular hgb is usually low in a condition called microcytosis, which occurs when the red blood cells are smaller than would be expected. As the cells themselves are small, their average amount of hemoglobin is low. A number of medical conditions can cause microcytosis. Iron deficiency anemia, which is having low numbers of red blood cells due to a lack of iron in the body, is the most common cause. Another cause of microcytosis is thalassemia, which is a genetic disease that makes the body produce abnormal hemoglobin.
On the other end of the spectrum, having a high mean corpuscular hgb is associated with macrocytosis. This condition occurs when the red blood cells are larger than they should be. One common cause of macrocytosis is megaloblastic anemia, which is having a low red blood cell count due to dietary deficiencies in vitamins such as folate or vitamin B12. Macrocytosis can also occur when the body is actively trying to make new red blood cells, and precursor cells called reticulocytes enter the body’s circulation. These reticulocytes are larger than mature red blood cells.