What is MCH? | Normal MCH levels chart | Factors that affect MCH | Low MCH | High MCH
Hemoglobin is essential for life. It’s an iron-rich protein molecule responsible for carrying oxygen from the lungs throughout the body and transporting waste carbon dioxide from the organs and tissues back to the lungs. Without enough hemoglobin, the body can’t get the oxygen it needs to function correctly, and this can lead to health problems such as heart failure, stroke, or anemia.
Healthcare providers can determine your average hemoglobin levels from a blood test called a complete blood count (CBC). A CBC consists of various lab tests that measure different parts of the blood, including red cells (or erythrocytes), white cells (or leukocytes), and platelets.
The information from the CBC allows healthcare providers to calculate your mean corpuscular hemoglobin (MCH). When used for diagnostic purposes, MCH is just one piece of the puzzle, but it’s important because it can give clues about iron deficiency, blood disorders, and other health conditions. Learn what an MCH test is and the meaning of different MCH levels.
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What is MCH?
MCH, or mean corpuscular hemoglobin, is a valuable part of a complete blood count (CBC). It’s a value representing the average amount of hemoglobin within a single red blood cell.
A complete blood count is a group of blood tests that measures:
- Red blood cells (which carry oxygen)
- White blood cells (which fight infections)
- Hemoglobin (a protein in red blood cells)
- Hematocrit (the proportion of red blood cells to plasma)
- Platelets (cells that form blood clots)
Healthcare providers may order this test during an annual checkup or to diagnose issues including infections, anemia, or certain cancers. It can also show how you are responding to medication.
Calculating the MCH from your complete blood count test results gives healthcare providers additional information about your blood and general health. It allows for further evaluation and can help with a diagnosis. MCH is related to two other values in a complete blood count:
- Mean corpuscular volume (MCV)
- Mean corpuscular hemoglobin concentration (MCHC)
These three measures are your red blood cell indices. They measure the size of your red blood cells and assess the amount of hemoglobin they contain. When there aren’t enough red blood cells or hemoglobin in your blood, you are anemic. Meaning, your blood is less able to carry oxygen. The result is that less oxygen reaches the tissues and organs, causing symptoms like fatigue, pale skin, and shortness of breath.
Normal MCH levels
Laboratories measure MCH in picograms (pg) per cell. The normal range of MCH values are between 27 and 31 pg per cell.
Individuals with certain health conditions may have MCH levels that are lower or higher than average. The table below shows what the different MCH levels could indicate. “Though different labs may have different reference ranges based on the local populations,” says Leann Poston, MD, a medical advisor for Impakt Fitness.
MCH levels chart |
||
|---|---|---|
| MCH level | Elevation | Meaning |
| Less than 26 pg per cell | Low | Potentially due to iron deficiency, nutrient deficiency, autoimmune disease, cancer, kidney disease, liver disease, blood loss, or thalassemia |
| 27 to 31 pg per cell | Normal | Commonly seen in healthy adults |
| Greater than 33.2 pg per cell | Elevated | Potential causes include vitamin B12 or folic acid deficiency, hemolysis, recovery after bleeding or chemotherapy or nutrient replacement, medication side effects, alcohol, liver disease, HIV, bone marrow disease, cancer, hypothyroidism, Down syndrome, copper deficiency, bariatric or other gastrointestinal surgery, kidney disease, congenital heart defects, and lung disease such as chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis |
Factors that affect MCH
Various health conditions can affect MCH levels. For example, anemias driven by deficiencies in iron can result in low MCH levels. Certain medical conditions can also lead to low MCH. These include thalassemia, an inherited blood disorder that is caused by defects in the hemoglobin genes. Additionally, women’s MCH may be lower than men’s because of blood loss during menstruation, which can lead to iron deficiency.
Conversely, individuals may have high MCH levels if they have a deficiency in nutrients such as vitamin B12 or folic acid. Medical conditions, such as alcoholism, liver disease, and bone marrow diseases, can also cause high MCH. Even medications, including metformin and Prilosec (omeprazole), can be associated with elevated MCH values.
RELATED: Anemia treatments and medications
Low MCH levels
Healthcare providers consider a value of less than 26 pg per cell as low MCH.
Causes
“MCH may be low either because the red blood cell is small or the cell has a lower-than-normal amount of hemoglobin in it,” Dr. Poston says. Several types of anemia can be associated with low MCH levels. These are the microcytic anemias, referring to the abnormally small red blood cells that can’t take in much hemoglobin. The common causes include malnutrition or nutritional and iron deficiencies. Because the body needs iron to make hemoglobin, iron deficiency can lead to anemia and low MCH levels.
People may have a higher risk of iron-deficient anemia if they:
- Bleed a lot during menstruation
- Bleed from other medical conditions
- Are pregnant
- Gave birth recently
- Have low dietary iron, particularly vegans and vegetarians
- Have peptic ulcer disease
- Are healing following trauma or surgery
Individuals who cannot absorb iron may also have low MCH levels. Low MCH levels are not necessarily serious, but they indicate an underlying problem that requires attention. These include people with celiac disease, inflammatory bowel disease such as Crohn’s disease, or who’ve had gastric bypass surgery. These three gastrointestinal conditions can actually lead to nutritional deficiencies associated with either high or low MCH levels.
Symptoms
If someone has low MCH, their red blood cells carry less oxygen throughout the body, leading to fatigue. “The symptoms of low MCH match symptoms associated with anemia,” says Dr. Poston. They include:
- Fatigue
- Shortness of breath
- Muscle weakness
- Tachycardia or fast heartbeat
- Low blood pressure
- Paleness
- Bruising easily
- Brittle nails
- Hair loss
Treatments
Treatment depends on the underlying cause of low MCH. “Low MCH level resulting from thalassemia may not require a treatment,” says Daniel Boyer, MD, a researcher at the Farr Institute in West Des Moines, Iowa. Conversely, “Severe symptoms of low MCH may require a blood transfusion to improve.”
Low MCH levels often occur because of iron deficiency that leads to anemia. For iron-deficiency anemias, healthcare providers may prescribe an iron supplement. They may also recommend including more iron-rich foods in your diet, such as red meat, fish, shellfish, and eggs. Vegans and vegetarians can also boost their iron intake with dark leafy vegetables, beans, lentils, tofu, and iron-fortified bread and cereals.
Additionally, people must ensure they eat enough vitamin B6 (pyridoxine) in their diet. The body needs this water-soluble vitamin to make red blood cells as it aids in converting iron to hemoglobin. It’s also essential to eat enough vitamin C through food or supplements to help the body absorb iron. People may also need to cut down on drinking black tea and coffee as the tannins can lower iron absorption.
If chronic blood loss is the cause of iron deficiency and the resultant anemia, addressing the source of bleeding is paramount. For instance, a stomach ulcer may require treatment including starting a proton pump inhibitor (PPI), such as Nexium (esomeprazole).
People with low MCH levels should seek professional medical advice and discuss a treatment plan with their healthcare provider before changing their diet or taking any iron supplements. If someone doesn’t have low iron levels, supplements could harm them.
High MCH levels
“An MCH value that is above 33.2 pg is considered high,” Dr. Boyer says.
Causes
“Often high MCH is caused by a B12 or folate deficiency, which is needed for the production of red blood cells or when the body is poorly absorbing these vitamins,” Dr. Boyer says.
These B vitamin deficiencies may happen if an individual:
- Can’t absorb vitamin B12 due to pernicious anemia, an autoimmune condition
- Can’t absorb vitamin B12 or folate due to a gastrointestinal disorder, such as celiac or inflammatory bowel disease
- Has all or part of their stomach removed in a gastrectomy procedure
- Eats a vegan or vegetarian diet as plants are low in B12
- Is malnourished
- Takes a medication that limits absorption or reduces levels of B12 or folate
High MCH levels often coincide with macrocytic anemia, which means the red blood cells are abnormally large, and there are fewer of them. Red blood cells usually measure between 80–100 femtoliter (fL). If they’re larger than 100 fL, they’re considered macrocytic.
Although it may seem that larger red blood cells would carry more hemoglobin, the opposite is true; they carry less. Having fewer cells with a lower oxygen-carrying capacity results in a low blood hemoglobin concentration or anemia.
Macrocytic anemia isn’t a single disease. Instead, it’s an umbrella term for various red blood cell abnormalities that are symptoms of certain medical conditions and nutritional problems. An example of a common macrocytic anemia is megaloblastic macrocytic anemia. Megaloblastic anemia happens when red blood cells cannot produce DNA quickly enough to divide at the correct time, and so they continue to grow and become too large. Vitamin B12 and folate deficiencies are two common causes of megaloblastic anemia.
Other potential reasons for high MCH include:
- Kidney and liver disease
- Down syndrome
- Myelodysplastic syndrome, a stem cell disorder
- Excessive alcohol intake
- Congenital heart defects
- Infections
- Cancer
- Thyroid dysfunction
- Lung disease
- Estrogen medications
Some medications can also change fluctuations in MCH levels, including:
- Anti-inflammatories
- Diuretics
- Antiretroviral drugs
- Anticonvulsants
- Some cancer medications
- Proton pump inhibitors, such as Prilosec
- Metformin, a common medication for Type 2 diabetes mellitus
Symptoms
People may not feel ill if their MCH is high. However, high MCH can mean that red blood cells aren’t dividing correctly, leading to macrocytic anemia. Therefore, symptoms may resemble those of low MCH.
With macrocytic anemia, an individual may experience a pattern of gradually worsening symptoms. Fatigue is a common symptom, and others include:
- Shortness of breath
- Very pale or yellow skin
- Headache
- Chest pain
- Fast heartbeat
- Weakness
- Poor concentration
- Confusion
Depending on the underlying cause, individuals with macrocytic anemia may experience digestive issues, such as low appetite, weight loss, and diarrhea. If an individual has a vitamin B12 deficiency, they may experience:
- Numbness or “pins and needles” in the extremities
- Balance problems
- Muscle weakness
- Confusion
- Memory loss
- Depression
- Mood problems
- Smooth or swollen tongue
- Nausea and vomiting
- Heartburn
- Diarrhea
- Loss of appetite
- Weight loss
Treatments
Again, the treatment of high MCH depends on the underlying cause and may differ for each person.
Dr. Boyer says, “Eating foods that are rich in vitamin B12 or folate, including brown rice, dark-green leafy vegetables, and white or red meat,” is one way to address high MCH levels if it is caused by a deficiency in these nutrients.
Although a varied and balanced diet provides these vitamins, in some cases, healthcare providers may prescribe injectable B12 (cyanocobalamin) or oral vitamin B12 or folate supplements if an individual isn’t absorbing vitamins effectively.
If the macrocytic anemia has another underlying cause, treating that primary problem can lead to improvement in the anemia. For example, correcting low thyroid hormone levels in hypothyroidism with Synthroid (levothyroxine) may resolve the anemia as well.
