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MCH Blood Test: High & Low Levels + Normal Range

Written by Biljana Novkovic, PhD | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

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Mean corpuscular hemoglobin (MCH) measures the amount of hemoglobin in your red blood cells. It can be used to help diagnose blood and iron-related disorders. Keep reading to learn more about the causes of low and high MCH and what you can do to address abnormal levels.

What is Mean Corpuscular Hemoglobin (MCH)?

Mean corpuscular hemoglobin (MCH) is a measure of the average amount of hemoglobin in your red blood cells. Hemoglobin is the protein that stores (binds) oxygen, which is what allows your blood to transport oxygen throughout your body [1, 2].

MCH is normally part of a complete blood count, which measures your hemoglobin, hematocrit, and red blood cell count. Doctors can use MCH to help diagnose different types of anemia [1, 2].

MCH values usually (but not always) parallel those of mean corpuscular volume (MCV), which is a measure of the size of your red blood cells. This means that when your red blood cells increase, MCH usually follows [1]. This makes sense because bigger red blood cells can fit in more hemoglobin.

Normal Range of MCH

The normal range of MCH is usually from 27 – 31 pg [1].

However, what your labs report as a normal range may differ slightly. Some lab-to-lab variability occurs due to differences in equipment, techniques, and chemicals used.

If your value is normal, that doesn’t mean you don’t have a condition such as anemia. There are anemias in which red blood cell size and hemoglobin content are normal (normocytic anemia) [3]. Your doctor will interpret your results in conjunction with your medical history and other test results.

Low MCH

A low mean corpuscular hemoglobin (MCH) means that your red blood cells contain less hemoglobin than normal. This usually also means they are smaller than normal (microcytic) [1].

People with small red blood cells (microcytosis) often do not show any symptoms unless their anemia is severe. Other blood tests can help your doctor determine the cause of microcytosis, such as MCV, RDW, and iron markers [4].

Causes of Low MCH

Causes shown below are commonly associated with low MCH. Work with your doctor or other health care professional to get an accurate diagnosis of the underlying cause.

1) Iron Deficiency

Iron deficiency is one of the most common causes of low MCH [5, 6, 7].

In a study of 830 subjects, 82% of the people who were iron deficient also had low MCH [8].

Iron deficiency is usually due to [5, 6, 9, 10]:

  • Dietary deficiency
  • Gut disorders that decrease nutrient absorption (including that of iron)
  • Toxins that interfere with iron absorption, such as lead

2) Thalassemia

Thalassemia, an inherited blood disorder with abnormal hemoglobin in the blood, also causes low MCH [11, 12].

Increasing MCH

Work with your doctor to determine and treat the cause of low MCH. Attempting to raise MCH artificially may not address underlying health conditions and ultimately may do more harm than good. If you have a low MCH, your doctor may order additional tests and/or use this result to help make a diagnosis and determine an appropriate course of action, which may or may not include the strategies below.

Diet

Check your iron levels. Make sure you are eating a healthy and nutritious diet in order to prevent iron deficiency. The foods rich in iron include liver, meat, fish, eggs, tofu, beans, nuts, seeds, whole grains, and dried fruits [5, 6, 13]. However, remember that nutrient deficiencies can also have non-dietary causes, such as bleeding or gut issues (malabsorption), in which case they can’t be corrected by simple dietary adjustments.

Coffee and tea can lower hemoglobin levels by decreasing the absorption of iron into the body. If you have low MCH, you may choose to reduce your intake of caffeine [14, 15].

Finally, vitamin C can significantly increase the absorption of iron from foods. If your iron is low, it’s a good strategy to combine your iron-rich meals with vitamin C sources such as lemon or orange juice. In addition, you can sprinkle lemon juice on your meat and salads [16].

High MCH

A high mean corpuscular hemoglobin (MCH) means that your red blood cells contain more hemoglobin than normal. This usually also means that they are larger than normal (macrocytic) [1].

By themselves, large red blood cells (macrocytosis) don’t seem to cause any symptoms. However, a diagnosis of macrocytosis can help provide information about underlying health conditions that may require treatment [17].

Causes of High MCH

Causes shown below are commonly associated with high MCH. Work with your doctor or other health care professional for an accurate diagnosis of the underlying cause.

1) Anemia due to Vitamin B12 or Folate Deficiency

One of the most common causes of high MCH is megaloblastic anemia. Megaloblastic anemia is often caused by folate (vitamin B9) or vitamin B12 deficiency and may be treated with supplements of the deficient nutrient [1, 18].

2) Heavy Alcohol Intake

Heavy alcohol intake increases MCH levels. Chronic alcohol users have significantly higher MCH levels than non-drinkers [19, 20, 17].

Decreasing MCH

Work with your doctor to determine and treat the cause of high MCH. Attempting to lower MCH artificially may not address underlying health conditions and ultimately do more harm than good. If you have high MCH, your doctor may order additional tests and/or use this result to help make a diagnosis and determine an appropriate course of action, which may or may not include the strategies below.

Diet

People who have megaloblastic anemia are often advised to increase their consumption of foods rich in vitamin B12 and folate (vitamin B9). Folate is abundant in leafy green vegetables, while vitamin B12 is easiest to source from meat products including chicken, turkey, lamb, beef, and pork liver, and dairy products such as yogurt and milk [21, 22].

Check your vitamin B12 and folate levels and make sure you are eating a healthy and nutritious diet in order to prevent vitamin deficiency [1]. However, remember that nutrient deficiencies can also have non-dietary causes, such as gut issues (malabsorption), in which case they can’t be corrected by simple dietary adjustments.

Lifestyle

Reducing your alcohol intake can prevent your MCH from becoming too high. Heavy alcohol consumption can decrease folate and vitamin B12 levels. But alcohol can also be toxic to red blood cells in its own right [19, 20, 23, 24].

Smoking has also been linked to lower B12 and folate levels, which in turn are linked to megaloblastic anemia. Smoking is generally very bad for your health, and it may contribute to or aggravate low MCH as well [25, 26].

Supplements

If you are deficient in vitamin B12 or folate, taking supplements can increase your vitamin levels. Doctors often recommend these supplements to patients with megaloblastic anemia; talk to yours before supplementing [27, 28].

About the Author

Biljana Novkovic

Biljana Novkovic

PhD
Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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