MCH levels in blood test: What do they mean?

We have all heard of hemoglobin, and how we must make sure that the levels don’t drop too much. This is what MCH means essentially. MCH stands for Mean Corpuscular Hemoglobin, which also means the weight of the red blood cells of our body. The MCH refers to the amount of hemoglobin in a single red blood cell. And what is hemoglobin? It is the protein that is present in the red blood cells, and responsible for transporting oxygen in the body.

Besides MCH levels, blood tests also indicate MCV (Mean Corpuscular Volume) that checks the size of the red blood cells. There is also something called MCHC (mean corpuscular hemoglobin concentration) that assesses hemoglobin concentration in cells. All these three levels are called RBC indices.

What are MCH levels?

MCH or mean corpuscular hemoglobin (Hb) is the Hb content or weight of the red blood cells (RBC). “The value is expressed in picograms (pg). The normal reference ranges of this parameter are based on the demographics of the population. It is normally 27 to 33pg,” explains Hematopathologist Dr Vidisha Mahajan.

How are MCH levels determined?

Usually, all doctors order a Complete Blood Count (CBC) panel, which will screen you for various diseases such as anemia and other infections. MCH levels are a calculated parameter and are not directly detected by the machine. “It depends on the Hb concentration and the RBC count. MCH is calculated by dividing the amount of Hb in a given blood volume by the number of RBCs present,” says Dr Mahajan.

Causes of low MCH levels

Anemia or iron deficiency is the biggest cause of low MCH levels. Deviation from the normal reference range of MCH is seen in different types of anemia as iron is very important for hemoglobin. “It has to be correlated with other complete blood count parameters for defining the anemia subtype. When the Hb is reduced, the RBCs are examined under a microscope to look for the type of anemia. They become smaller with a pronounce central pallour in iron deficiency anemia. This is called hypochromia. The RBCs are larger and paler in B12 and folic acid deficiency type of anemia and are called macrocytic RBCs. Both these constitute nutritional anemias,” explains Dr Mahajan. The common causes of reduced MCH include:
• Iron deficiency anemia
• Anemia due to blood loss
• Anemia of chronic disease associated with infections, cancer and autoimmune diseases.
• Hemoglobinopathies like beta thalassemia

What are the symptoms of low MCH?

The symptoms of low MCH include:

• Shortness of breath
• Fatigue
• Dizziness and pallor
• Increased heart rate
• Chest pain
• Heart failure

Causes of high MCH levels

High MCH is seen in people with macrocytic anemia or large red blood cells. These are associated with deficiency of vitamin B 12 and folic acid.

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Symptoms of high MCH

The symptoms of high MCH (>33pg) include:

• Pallor or a pale appearance
• Fatigue
• Dizziness
• Shortness of breath
• Tachycardia

In vitamin B12 deficiency, there is numbness and tingling sensation in the feet and hands along with signs of mental confusion in the later stages. “There may be a red beefy appearance of the tongue. Folic acid deficiency may be associated with diarrhea and stomatitis,” says Dr Mahajan.

What does it mean to live with low or high MCH?

In cases of low or high MCH, the first step is to improve the diet to include foods rich in iron, vitamin B12 or folic acid. “Supplements in the form of oral or injectable drugs are available to treat if the symptoms are severe and require immediate correction,” explains Dr Mahajan.