What Does MCH on a Blood Test Mean?

Mean corpuscular hemoglobin (MCH) in a blood test refers to the average amount of hemoglobin in a person's red blood cells. Hemoglobin is a protein that carries oxygen around the human body. MCH is one of the standard measurements in a complete blood count test.

A blood sample being held with a row of human samples

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Definition of Hemoglobin

Before getting into the specifics of MCH levels in blood test results, it's important to understand that it is measuring the average amount of hemoglobin in a person's red blood cells, which are also known as erythrocytes. Human blood is made up of red blood cells, white blood cells, and platelets. Of those, red blood cells are responsible for carrying oxygen and carbon dioxide throughout the body.

Red blood cells carry a protein called hemoglobin, which contains iron. These red blood cells transport oxygen to the tissues throughout the human body, and waste (in this case, carbon dioxide) away from the tissues—which then leaves the body when it is exhaled through the lungs. When combined with oxygen, hemoglobin is what gives blood its red color.

How Hemoglobin Is Measured

A person's annual check-up with their general practitioner—or, when their doctor needs more information to help with a potential diagnosis—typically includes a blood test known as a complete blood count (CBC). Technically a series of multiple tests, the idea behind a CBC is to get information on three types of a patient's blood cells: red blood cells, white blood cells, and platelets.

A small sample of blood is required for a CBC and is typically drawn from a vein in a person's arm using a needle. While this is bearable for many people, others experience physical and/or mental discomfort when it comes to needles or drawing blood. Once this part is over, lab experts analyze the blood and provide a report to the physician who ordered the test.

When the results of a blood test are ready, they provide details on how many cells there are in the blood, and the physical characteristics of the cells, such as size, shape, and content. In a CBC, the mean corpuscular hemoglobin (MCH) measurement is the average amount of hemoglobin in a red blood cell.

A person's MCH value typically parallels their mean corpuscular volume (MCV) level, which measures the actual size of the red blood cells themselves. For this reason, a doctor may decide to skip this part of the CBC. But that doesn't mean MCH levels are useless: they also provide important information regarding whether anemia is hyper-, hypo-, or normal.

Understanding MCH in Test Results

If a doctor is using MCH levels to assist with making a diagnosis or simply learning more about a patient's health, they first look to see if it is in the normal range of 27 to 31 picograms/cell. There are specific symptoms and conditions associated with MCH levels that are both lower and higher than normal. Here is a general overview of what these levels can say about a person's health.

Low MCH Levels

Having MCH levels below 27 picograms/cell is most commonly associated with anemia. But in addition to anemia, it may also be a sign of conditions including:

  • Iron deficiency (almost always caused by blood loss)
  • Deficiency of other nutrients, such as vitamin B12 or folic acid
  • Internal or external blood loss resulting from surgery, injury, menstrual bleeding, or bleeding from the gastrointestinal tract
  • Cancer
  • Thalassemia (a common inherited blood disorder caused by genetic mutations in the hemoglobin genes)
  • Kidney disease
  • Autoimmune diseases
  • Liver disease

People with low MCH levels may experience symptoms including:

  • Fatigue
  • Pale skin (pallor)
  • Weakness
  • Dizziness
  • Shortness of breath
  • Cold hands and feet

High MCH Levels

Having MCH levels above 31 picograms/cell is most commonly associated with the following conditions:

  • Polycythemia vera (a rare blood disease typically caused by a genetic mutation where the bone marrow produces too many red blood cells)
  • Congenital heart defects
  • Certain types of kidney diseases, including kidney cancer
  • Lung disease, including chronic pulmonary obstructive disease (COPD) and pulmonary fibrosis

People with high MCH levels may experience symptoms including:

  • Headaches
  • Blurred or double vision
  • Dizziness
  • Itching
  • Blood clots

Treatment Options for Abnormal MCH Levels

If a patient's MCH levels appear to be higher or lower than normal, it will result in a discussion with their physician about what this means to their overall health—including potential treatment options, if necessary.

There are a variety of reasons why MCH levels may be outside the normal range, and it doesn't necessarily mean that a person has a serious illness or even cause for concern.

A Word From Verywell

Although there is a lot that doctors can learn about a person's health through a CBC—including their MCH levels—it is only one aspect of making an accurate diagnosis. Other factors, including family history, specific symptoms, and lifestyle also provide crucial information about a person's overall health and the likelihood of having a particular condition.

This requires open and honest conversations between health care professionals and patients in order to get a more complete picture of what may be causing a particular blood test result, including MCH levels.

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