MCHC Blood Test Results: Meaning of Low and High Levels

Mean corpuscular hemoglobin concentration (MCHC) measures the average hemoglobin concentration in a given volume of red blood cells. Hemoglobin is an iron-rich protein that carries oxygen to tissues.

An MCHC blood test may be used as a preliminary check for anemia and is part of a complete blood count (CBC) test. A normal MCHC value is 32 to 36 grams per deciliter (g/dL) or 320 to 360 grams per liter (g/L).

A higher or lower than normal MCHC value may indicate that you have a type of anemia, which means you have a low red blood cell count, but your healthcare provider may order more diagnostic tests to be sure.

Learn about MCHC's importance and what may cause a high or low MCHC value.

MCHC Results and What They Mean

A low MCHC (hypochromia) may mean that there is a lower concentration of hemoglobin within a given volume of red blood cells and, hence, a reduced capacity to carry oxygen to the body's tissues.

A high MCHC (hyperchromia) can mean that there is a higher hemoglobin concentration in red blood cells than usual.

Know, however, that your MCHC value may be normal with many types of anemia (normochromic anemias), such as:

• Blood loss anemia
• Anemia due to kidney disease
• Mixed anemias
• Bone marrow failure
• Hemolytic anemias (many types)

How MCHC Is Calculated

MCHC is calculated by multiplying the hemoglobin level times 10 and then dividing by the hematocrit level, which is the volume percentage of red blood cells in your blood. The number is recorded in grams per liter.

• MCHC = Hb x 10 / hematocrit

MCHC may also be calculated by dividing the mean corpuscular hemoglobin (MCH) (i.e., the average mass of hemoglobin in each red blood cell) by the MCV, the average size of the red blood cells:

• MCHC = MCH / MCV

Purpose of MCHC Blood Test

MCHC is a measure of the concentration of hemoglobin in red blood cells. Since hemoglobin is the molecule to which oxygen attaches, MCHC is a measure of the average oxygen-carrying capacity of the red blood cells circulating in the body.

The MCHC is done as part of a CBC, so the test is done any time a CBC is ordered. For example, this may be during routine health screenings or the diagnosis, treatment, and follow-up of a wide range of medical conditions.

A healthcare provider may specifically look at MCHC results:

• When symptoms of anemia are present, such as fatigue, pale skin, or light-headedness
• When looking for the different causes of anemia (when a person's red blood cell count and/or hemoglobin levels are low)

While the MCHC value is helpful in diagnosing anemia, it is also used along with the red blood cell count and other red blood cell indices, such as mean corpuscular volume (MCV) and red cell distribution width (RDW), to help diagnose other health issues.

What Causes a Low MCHC?

Possible causes of low MCHC include:

• Iron deficiency (with or without anemia)
• Lead poisoning
• Thalassemias (beta thalassemia, alpha thalassemia, and thalassemia intermedia)
• Sideroblastic anemia
• Anemia of chronic disease

A low MCHC without anemia is associated with poor outcomes for people in intensive care. It may also indicate iron deficiency before anemia develops.

What Causes a High MCHC?

There can be various reasons for a high MCHC. For instance, MCHC may be falsely increased due to cold agglutinin disease (CAD), a rare autoimmune disorder in which the body's immune system attacks red blood cells.

Potential causes of a high MCHC with anemia include:

• Autoimmune hemolytic anemia (due to medications, autoimmune conditions, and more)
• Hereditary spherocytosis
• Severe burns
• Liver disease
• Hyperthyroidism
• Sickle cell disease (homozygous)
• Hemoglobin C disease
  

Inaccurate MCHC Results

The MCHC is calculated from hemoglobin and hematocrit, so anything that interferes with these numbers will make the MCHC inaccurate. The following can affect the accuracy of your MCHC reading.

Blood Transfusion

Your MCHC reading after a blood transfusion may not accurately reflect the concentration in your red blood cells alone.

This is because blood drawn after a blood transfusion will be a mixture of donated cells plus a person's normal red blood cells.

Combined Anemia

If a person has two different types of anemia that lead to different MCHC levels, the reading won't be as helpful in diagnosing the type of anemia.

For example, the MCHC may be normal if a person has a combination of iron-deficiency anemia (which causes a low MCHC) and spherocytosis, a condition that causes red blood cells to be sphere-shaped (which tends to cause a high MCHC).

Health Conditions

Health conditions that affect hemoglobin or hematocrit levels can give a false MCHC result.

Conditions that can cause the hematocrit level to be falsely high and the hemoglobin levels to be falsely low include:

• Hyperlipidemia, an increased level of cholesterol or triglycerides
• Hyperbilirubinemia, elevated bilirubin levels in the blood, as with liver disease
• Autoagglutination, the clumping of red blood cells

With hemolysis (breakdown of red blood cells), free hemoglobin in the plasma leftover from the broken red blood cells will also cause an abnormal result—meaning the MCHC will be falsely increased.

MCHC Blood Test Procedure

You likely have gotten your MCHC checked without even realizing it, since it's part of routine blood work.

Here's a walk-through of how a sample of blood is drawn for testing.

Before the Test

There are no dietary or activity restrictions before having a CBC. It is important to bring your insurance card to your appointment and ensure your healthcare provider has access to prior CBCs you have had for comparison.

During the Test

The test can be conducted in many hospitals and clinics. Prior to drawing your blood, a lab technician will cleanse the area (usually a vein in the arm) with an antiseptic, and a tourniquet is applied to visualize the vein better. If you have a chemotherapy port, blood can be drawn directly from the port.

The technician will then insert the needle into a vein. You may feel a sharp poke when the needle enters and some pressure as it remains in place. Some people may feel lightheaded or faint with the needle stick. Make sure to let the technician know if you are feeling lightheaded.

After obtaining the sample, the technician will remove the needle and ask you to hold pressure over the site. When the bleeding has stopped, a bandage or gauze will be applied to your arm to keep the area clean and to reduce the chance of further bleeding.

After the Test

When the test is done, you will be able to return home and resume your regular activities. Potential side effects include:

• Pain from the needle stick, especially if a number of attempts are made
• Difficulty obtaining a specimen from a blood draw (such as in people whose veins are difficult to access due to chemotherapy)
• Bleeding (which can take longer to stop in people who are on blood thinners or have a bleeding disorder)
• Hematoma or a large bruise (can be uncomfortable, but it is very uncommon)
• Infection (when the needle is inserted, there is a small risk of bacteria being introduced into the body)
  

Complementary Tests

In addition to MCHC, a CBC provides a good amount of information about the body's cells, including the total number of red blood cells, white blood cells, and platelets, as well as the previously mentioned red blood cell indices:

• Mean corpuscular volume (MCV): The measure of the average size of the red blood cells
• Red cell distribution width (RDW): The number that reflects the variation in sizes of the red blood cells
• Mean corpuscular hemoglobin (MCH): The average mass of hemoglobin per red blood cell

Other tests may be done to further clarify information found on the CBC and help diagnose a specific type of anemia. These tests include:

• Peripheral blood smear for morphology: A peripheral smear involves looking at the blood sample under the microscope. This allows the lab professional to directly visualize other changes in the red blood cells that may be associated with anemia, such as target cells, nucleated red blood cells, and more.
• Iron studies: Serum iron and iron-binding capacity and/or ferritin levels can give valuable information on iron stores and can help discriminate iron deficiency from other anemias with a low MCHC.
• Vitamin B12 level: Vitamin B12 levels are helpful in looking for pernicious anemia.
• Bone marrow aspiration and/or biopsy: In some cases, a bone marrow study may be needed to assess the appearance of blood cells in the bone marrow and iron stores.
  

Summary

Mean corpuscular hemoglobin concentration (MCHC) is a measure of the concentration of hemoglobin in red blood cells. It is a value seen on a complete blood count (CBC), which includes information about the total number of red blood cells, white blood cells, platelets, and other red blood cell indices.

A normal MCHC value is typically in the range between 32 g/dL to 36 g/dL (320 g/L to 360 g/L). A higher or lower than normal MCHC may indicate a type of anemia.

The MCHC test is most meaningful when combined with other results on a CBC and can be helpful in discovering causes of anemia as well as predicting prognosis in those without anemia.

When using these results, however, it is very important to be aware of the limitations as well as the potential for error. It is best to consider any findings only after they are repeated and supported by other tests.