Mean Corpuscular Hemoglobin, or MCH, is a measurement obtained during a routine Complete Blood Count (CBC) test. This value provides information about your red blood cells, which transport oxygen throughout the body. The MCH result is one part of a panel of tests, often referred to as red blood cell indices, that healthcare providers use to assess overall blood health and screen for conditions like anemia.
What MCH Measures
The MCH value quantifies the average mass, or weight, of hemoglobin contained within a single red blood cell. Hemoglobin is the iron-containing protein that binds to oxygen in the lungs and releases it into the body’s tissues. To calculate MCH, laboratory machines divide the total mass of hemoglobin in a blood sample by the total number of red blood cells present.
The resulting value is typically reported in picograms (pg) per cell. For adults, the generally accepted normal reference range for MCH is between 27 and 33 picograms, though this range may vary slightly between laboratories. This measurement helps medical professionals classify the type of anemia present, as the amount of hemoglobin usually correlates with the cell’s size.
Understanding Low MCH Results
A low MCH result, often considered below 27 picograms, indicates that the red blood cells are carrying a lower-than-average amount of hemoglobin. This condition is medically described as hypochromia, meaning the cells appear paler than normal because they lack sufficient hemoglobin. A low MCH suggests microcytic anemia, characterized by red blood cells that are smaller than usual.
The most common reason for this finding is iron deficiency anemia, as iron is required for the body to synthesize hemoglobin. Insufficient iron intake, chronic blood loss, or poor iron absorption can all lead to this deficiency. Other potential causes include genetic conditions like thalassemia, where the body’s ability to produce hemoglobin is limited. Symptoms associated with low MCH often include general fatigue, paleness of the skin, or shortness of breath due to reduced oxygen delivery to tissues.
Understanding High MCH Results
An MCH result that measures above the normal range, generally over 33 picograms, signifies that the red blood cells contain more hemoglobin than average. This increase in hemoglobin weight is usually due to the red blood cells themselves being larger than normal, a condition called macrocytosis. When this macrocytosis is also accompanied by anemia, it is classified as macrocytic anemia.
The primary causes for macrocytic anemia and a high MCH are deficiencies in Vitamin B12 and folic acid. These two B vitamins are necessary coenzymes for proper DNA synthesis, which is required for red blood cell division. When B12 or folate is lacking, the bone marrow produces red blood cells that cannot divide properly, resulting in fewer, but significantly larger, cells. High MCH can also be linked to other health issues like chronic liver dysfunction or excessive alcohol use.
Steps Following an Abnormal MCH Test
If an MCH level is found to be outside the normal range, a physician will not rely on this single number for diagnosis, but will consider it alongside other indices like Mean Corpuscular Volume (MCV). The next step involves ordering targeted follow-up blood work to identify the specific underlying cause.
For a low MCH, tests may include checking serum iron, ferritin (which measures stored iron), and total iron-binding capacity. If a high MCH is detected, the doctor will likely request specific blood tests for Vitamin B12 and folate levels. Once the cause is pinpointed, treatment focuses on correcting the deficiency or managing the underlying condition. This can involve dietary changes, taking nutritional supplements like iron or B vitamins, or addressing chronic conditions such as liver or kidney disease.