Understanding Mean Corpuscular Hemoglobin (MCH)

What Exactly is MCH?

Mean corpuscular hemoglobin (MCH) is a measurement that reflects the average mass of hemoglobin inside your red blood cells. Normal red blood cells contain about 27-31 picograms of hemoglobin. MCH levels quantify the concentration of hemoglobin in an individual red cell, reported in picograms per cell.

Along with other red blood cell (RBC) metrics like MCV and RDW, tracking the MCH gives healthcare providers important clues in diagnosing different types of anemia or other hematologic disorders. Let’s explore what MCH indicates, possible high or low values, and how it differs from related measurements.

Why Do Doctors Assess Your MCH Levels?

There are a few key reasons your doctor may order an MCH test:

• Diagnose Different Types of Anemia – One of the most common applications is using MCH to differentiate between microcytic and macrocytic anemias. Low MCH often indicates iron deficiency anemia while elevated levels suggest macrocytic anemia from vitamin deficiencies.
• Monitor Anemia Treatment – Repeating the MCH test allows assessment of whether iron, vitamin B12, folate, or other anemia treatments are working. Improving MCH levels show the bone marrow is responding appropriately.
• Evaluate Hemoglobin Function – Since MCH measures hemoglobin concentration in each cell, it reflects how well your body produces and utilizes this oxygen transport protein. Declining MCH may signify abnormal hemoglobin function.
• Screen for Hematologic Disorders – Unusual high or low MCH readings can uncover other blood conditions like thalassemias, bone marrow dysfunction, sideroblastic anemia, and lead exposure. Your doctor may recommend more testing.

High MCH Levels and What They Mean

What causes elevated MCH readings outside the normal range? High MCH relates to an increased concentration of hemoglobin within your red blood cells. Some potential reasons for high MCH include:

• Vitamin B12/Folate Deficiency – The most common cause of high MCH is a type of anemia stemming from inadequate vitamin B12 or folate. Since these vitamins are required for RBC production, deficiencies restrict cell creation in the bone marrow, releasing fewer but hemoglobin-rich reticulocytes into circulation.
• Retics High in Hemoglobin – Even if the actual number of reticulocytes is normal on your complete blood count report, they contain excess hemoglobin in vitamin deficiency anemias. This phenomenon explains elevated MCH despite overall low red cell counts.
• Liver Disease – Sometimes cirrhosis, viral hepatitis and other liver conditions increase MCH. The mechanism is not always clear but may relate to accompanying folate deficiency or increased hemoglobin synthesis.
• Bone Marrow Disorders – Certain bone marrow diseases like the preleukemic state of myelodysplastic syndrome can initially boost hemoglobin concentration inside red cells. Later the MCH declines with worsening, ineffective erythropoiesis.

Consequences of High MCH Values

What ramifications does high MCH have? In some mild to moderate cases without marked anemia, there may be limited symptoms. However, chronically elevated MCH from untreated vitamin deficiencies or other diseases can lead to:

• Fatigue, Weakness from Anemia – As fewer circulating red cells transport oxygen vital for energy production, patients experience severe tiredness, reduced endurance, shortness of breath and even palpitations.
• Bleeding Issues – With giant, structurally abnormal red cells from certain disorders, elevated MCH raises the risk of harmful blood clots or hemorrhage.
• Heart Complications – To compensate for lower oxygen carrying capacity with fewer cells, the heart pumps faster trying meet bodily demands, causing arrhythmias.

Low MCH Levels: Causes and Implications

In contrast, decreased MCH corresponds to a diminished concentration of hemoglobin inside red blood cells. What are some reasons your MCH may drop below the expected range?

• Iron Deficiency Anemia – This extremely common cause of microcytic anemia develops from chronic blood loss, pregnancy, menstruation or poor iron intake. Declining iron hinders hemoglobin output, reducing MCH.
• Thalassemia Traits – Alpha and beta thalassemias are inherited blood conditions affecting either hemoglobin production or structurally abnormal hemoglobin function. Destruction of faulty hemoglobin results in small RBCs with low hemoglobin content.
• Chronic Inflammation – With disorders like rheumatoid arthritis, inflammatory bowel disease and certain cancers, cytokines hamper iron absorption and alter erythropoietin red cell production signals, lowering MCH. This contributes to “anemia of chronic disease.”
• Lead Exposure – Lead toxicity can manifest with microcytic anemia and decreased MCH even prior to symptoms. Children are especially vulnerable to environmental lead ingestion which impairs several enzymatic steps in hemoglobin synthesis.

Consequences of Diminished MCH

What effects stem from reduced hemoglobin concentration within red cells? It depends on the severity of the anemia and underlying cause, but repercussions from critically low MCH include:

• Fatigue, Weakness, Dizziness – Impaired oxygen carrying capacity with small, hemoglobin depleted RBCs substantially decreases energy delivery to tissues resulting in constitutional symptoms.
• Organ Damage – Prolonged, severe tissue hypoxia can precipitate eventual heart, liver, kidney and neurological complications. Children’s growth delays with iron deficiency anemia.
• Pica, Restless Legs – The profound iron deficient state driving declines in hemoglobin and thus MCH manifests with unusual cravings for dirt, paper, ice evident in pica. Many also experience unpleasant restless limb sensations.
• Increased Infections – Chronic anemia impairs immune cell maturation and function, elevating infection risk. This worsens the cycle of inflammation perpetuating disease like rheumatoid arthritis.

Key Differences Between Hemoglobin and MCH

Hemoglobin and MCH both relate to hemoglobin but represent distinct metrics:

• Hemoglobin – Quantifies total circulating hemoglobin level expressed in grams per deciliter, reflecting overall oxygen carrying capacity by all red cells.
• MCH – Specifically measures picograms of hemoglobin inside an average individual red blood cell. Lower in iron deficiency and thalassemia microcytic anemias.

While total blood hemoglobin levels may remain normal with high RBC counts like in thalassemias, MCH detects inadequate hemoglobin incorporation inside each small erythrocyte. Doctors assess both, but MCH provides unique, additional information.

Contrasting MCH and MCHC

MCHC or mean corpuscular hemoglobin concentration also traces hemoglobin content but differs from MCH:

• MCHC – The proportion of hemoglobin relative to total RBC volume, reported as a percentage concentration. MCHC changes mirror MCH.
• MCH – Absolute hemoglobin mass per cell in picograms. MCH more specifically quantifies degree of anemia for classification and treatment monitoring.

For anemia evaluation, MCH supersedes MCHC in utility. Yet as complementary red cell indices, both aid diagnosis when incorporated together with history, symptoms and other lab findings.

Interpreting MCV and MCH Together

MCV meaning mean corpuscular volume measures the average size of red cells. Evaluating MCV and MCH indices in tandem better identifies patterns consistent with certain diseases:

• Low MCV, Low MCH – Suggests iron deficiency anemia or thalassemias. Presents with microcytic, small red cells having reduced hemoglobin.
• High MCV, High MCH – Occurs in vitamin deficiency macrocytic, larger anemias with elevated hemoglobin concentration per cell. Also liver disease.

Tracking simultaneous MCV and MCH directional changes expands diagnostic discrimination between various anemia subtypes more than either value independently. This aids doctors selecting appropriate treatments.

What Disorders Lower MCH?

Many diverse medical conditions lead to decreased MCH values mainly by impaired hemoglobin incorporation into erythrocytes. Some prominent diseases associated with low MCH include:

• Iron deficiency anemia
• Thalassemias
• Anemia of chronic disease
• Lead poisoning
• Sideroblastic anemia
• Bone marrow failure disorders
• Erythropoietin deficiency
• Hemoglobinopathy disorders

Paying attention to accompanying symptoms helps differentiate these entities. Always discuss unusual hematology results including MCH with your doctor for proper workup and management.

Normal Reference Range

Typical laboratory reference standards for normal MCH in adults fall between:

• 27 to 31 picograms/cell (SI Units)
• 27 to 34 picograms/cell (Conventional Units)

Remember MCH levels outside expected norms strongly suggests potential anemia necessitating further evaluation of red cell size, number and various nutritional markers tailoring treatment.

Managing Elevated MCH

No direct MCH lowering treatments exist apart from addressing any underlying diseases. However, for suspected vitamin deficiencies provoking increased MCH:

• Oral/Injectable Vitamin B12 – Cyanocobalamin or hydroxycobalamin formulations treat pernicious anemia from B12 deficiency.
• Folic Acid Supplements – Oral folic acid or prescription folate helps correct folate deficiency anemia manifestations like elevated MCH.

Monitoring MCH guides treatment response in macrocytic anemias. Beyond supplementation, severe anemia warrants possible erythropoietin stimulating agents or transfusions for symptomatic relief preserving tissue oxygenation.

The Bottom Line

In summary, MCH provides a measurement of the average hemoglobin content in red blood cells, serving as a useful biomarker for detecting and differentiating anemia to best guide management. Evaluating MCH within the context of a patient’s complete blood count gives the most helpful clinical insights. Calculate where your MCH level falls relative to the reference range and discuss the implications at your next hematology visit.