Mean Corpuscular Volume (MCV)
Other names: Mean RBC Volume, MEAN CORP. VOLUME, Mean Cell Volume
What is Mean corpuscular volume (MCV)?
Mean corpuscular volume (MCV) is the average volume (one can also say average size) of red cells in a specimen. MCV is elevated or decreased in accordance with average red cell size; ie, low MCV indicates microcytic (small average RBC size), normal MCV indicates normocytic (normal average RBC size), and high MCV indicates macrocytic (large average RBC size).
When is the Mean corpuscular volume (MCV) calculated?
Mean corpuscular volume (MCV) is a value calculated during a routine blood test called a complete blood count (CBC). An MCV is routinely performed by an automated machine on all CBCs. It’s included in the portion of the CBC that provides information on your red blood cells in particular, called the RBC (red blood cell) indices.
There are three main types of corpuscles (blood cells) in your blood: red blood cells, white blood cells, and platelets.
An MCV blood test measures the average size of your red blood cells, also known as erythrocytes. Red blood cells move oxygen from your lungs to every cell in your body. Your cells need oxygen to grow, reproduce, and stay healthy.
If your red blood cells are too small or too large, it could be a sign of a blood disorder such as anemia (=a condition in which the body does not have enough healthy red blood cells), a vitamin deficiency, or other medical condition.
MCV is usually not interpreted as an isolated measurement. Rather, it is compared to the results of your other RBC indices and CBC values, like hemoglobin and hematocrit. Your doctor will also consider any symptoms or changes in your health when interpreting these test results.
MCV, along with mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC), is a part of RBC indices (erythrocyte indices), which are measurements and/or calculations for determining the size, content, and hemoglobin concentration.
More recently, red cell distribution width (RDW) has also been included as a part of RBC indices. The indices are useful in the morphologic characterization of anemia. Among these parameters, MCV is the most useful value used to classify the type of anemia based on red cell morphology.
Why is the Mean corpuscular volume (MCV) important to measure?
Your red blood cells carry oxygen throughout your body. This oxygen, in turn, powers your cells. The characteristics of your red blood cells -- including size -- provide information about how successfully they can transport oxygen.
An MCV blood test is helpful because having a large number of atypically large or atypically small red blood cells can indicate certain conditions. It is less helpful if you have a wide variety of red blood cell sizes in a blood sample. In that case, even if there’s an abnormality, the numbers may average out as normal.
What is a normal MCV level?
A typical adult MCV level is 80–100 femtoliters (fl).
- However, typical ranges vary between age groups and sexes.
- MCV results may differ among labs, so people should not worry if their reading is slightly above or below these ranges.
- If you have anemia or other health conditions you can have normal or abnormal MCV results. It is also possible for healthy people to have a normal or abnormal MCV result.
In people with anemia, MCV results are categorized as follows:
- Low MCV means that RBC are smaller than normal and may indicate microcytic anemia. This condition may be caused by iron deficiency, lead poisoning, or thalassemia, a genetic condition that causes your body to have less hemoglobin than normal.
- Normal MCV may indicate normocytic anemia. This can occur when an individual experiences symptoms of anemia due to sudden blood loss, kidney failure, or aplastic anemia, a rare disorder where the body does not produce enough RBC.
- High MCV means that the RBC are too large and indicates macrocytic anemia. This condition can be caused by several factors including low folate or vitamin B12 levels or chemotherapy.
Main types of anemia classified based on red cell morphology and their common causes:
Common causes of microcytic and hypochromic anemia (decreased MCV and MCH) are as follows:
- Iron deficiency anemia
- Anemia of chronic disease
- Thalassemia
- Sideroblastic anemia
Common causes of macrocytic anemia (increased MCV) are as follows:
- Folate deficiency anemia
- Vitamin B12 deficiency anemia
- Liver disease
- Hemolytic anemias
- Hypothyroidism
- Excessive alcohol intake
- Aplastic anemia
- Myelodysplastic syndrome
Common causes of normocytic and normochromic anemia (normal MCV) are as follows:
- Anemia of chronic disease
- Acute blood loss
- Hemolytic anemia, such as autoimmune hemolytic anemia, hereditary spherocytosis, or nonspherocytic congenital hemolytic anemia (G6PD deficiency, other)
- Anemia of renal disease
- Aplastic anemia
Additional notes: when considering the causes of anemia, the guidelines above are helpful but have limitations. For example, hemolytic anemia and aplastic anemia can manifest as normochromic and normocytic anemia or macrocytic anemia; anemia of chronic disease can be normochromic and normocytic anemia or microcytic anemia; sideroblastic anemia can be microcytic anemia, macrocytic anemia, or normochromic and normocytic anemia (due to the presence of dimorphic population of microcytes and macrocytes).
In addition, once the causes of anemia are considered, correlation with clinical findings, including history and physical examination, is important, as is, when necessary, performing more definitive tests to arrive with a definitive diagnosis.
References:
American Society of Hematology [Internet]. Washington D.C.: American Society of Hematology; c2022. Anemia https://www.hematology.org/education/patients/anemia
Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Red Cell Indices; 451 p.
Maner BS, Moosavi L. Mean Corpuscular Volume. https://www.ncbi.nlm.nih.gov/books/NBK545275/
National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; How Are Thalessemias Diagnosed? https://www.nhlbi.nih.gov/health/health-topics/topics/thalassemia/diagnosis
National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Iron Deficiency Anemia https://www.nhlbi.nih.gov/health-topics/iron-deficiency-anemia
Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Anemia https://www.testing.com/anemia-testing/
Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Complete Blood Count (CBC) https://labtestsonline.org/understanding/analytes/cbc/tab/test
Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. MCV Test; Available from: https://www.testing.com/tests/mcv-test/
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Complete Blood Count with Differential https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=complete_blood_count_w_differential
Yang, J., Yan, B., Yang, L. et al. Macrocytic anemia is associated with the severity of liver impairment in patients with hepatitis B virus-related decompensated cirrhosis: a retrospective cross-sectional study. https://doi.org/10.1186/s12876-018-0893-9
MedlinePlus: National Library of Medicine. Red Blood Cell (RBC) Indices. https://medlineplus.gov/lab-tests/red-blood-cell-rbc-indices/
Merritt BY, Curry CV. Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC) In: Wheeler TM, ed. https://emedicine.medscape.com/article/2054497-overview
National Heart, Lung, and Blood Institute. Blood Tests. https://www.nhlbi.nih.gov/health-topics/blood-tests
Braunstein EM. Evaluation of Anemia. Merck Manual Professional Edition https://www.merckmanuals.com/professional/hematology-and-oncology/approach-to-the-patient-with-anemia/evaluation-of-anemia
Centers for Disease Control and Prevention. Blood and Urine Collection. https://www.cdc.gov/nchs/data/nhanes/nhanes_09_10/labcomp_f.pdf
George TI. Automated Hematology Instrumentation. In: Uhl L, ed. UpToDate. https://www.uptodate.com/contents/automated-hematology-instrumentation
What does it mean if your Mean Corpuscular Volume (MCV) result is too high?
High MCV: Understanding Macrocytic Anemia and Its Causes
A high mean corpuscular volume (MCV) indicates that red blood cells are larger than normal, a condition known as macrocytic anemia. This type of anemia is often linked to vitamin deficiencies, underlying medical conditions, or lifestyle factors.
One subtype, megaloblastic anemia, commonly arises from deficiencies in vitamin B12 (cobalamin) and folate (vitamin B9). Both vitamins are essential for DNA synthesis, and their deficiency disrupts normal red blood cell production, leading to the formation of larger, immature cells.
Causes of High MCV
High MCV levels can occur due to various conditions, with prevalence increasing with age. About 30% of older adults exhibit elevated MCV without an identifiable cause. Here are the most common causes:
Vitamin Deficiencies
- Vitamin B12 Deficiency: Often caused by poor absorption due to age, gastrointestinal disorders (e.g., pernicious anemia, Crohn's disease), or a lack of dietary intake.
- Folate Deficiency: Results from poor diet, certain medications (e.g., methotrexate, anticonvulsants), or increased demand, such as during pregnancy.
Liver-Related Causes
- Liver Disease: Impaired liver function affects red blood cell production, resulting in larger cells.
- Alcoholism: Alcohol disrupts bone marrow function, contributing to macrocytosis.
Endocrine and Autoimmune Disorders
- Hypothyroidism: Low thyroid hormone levels are associated with mild macrocytosis.
- Cold Agglutinin Disease: An autoimmune condition targeting red blood cells.
Bone Marrow Disorders
- Myelodysplastic Syndromes (MDS): A group of conditions where bone marrow produces abnormal, dysfunctional blood cells, often referred to as "preleukemia."
- Aplastic Anemia: A rare disorder where the bone marrow fails to produce sufficient new blood cells.
Other Common Causes
- Hemolytic Anemias: These conditions cause premature destruction of red blood cells, prompting the production of larger, immature cells.
- Chemotherapy Drugs: Medications that interfere with DNA synthesis can result in macrocytosis.
- Chronic Hypoxia: Low oxygen levels, often seen in chronic obstructive pulmonary disease (COPD), can cause larger red blood cells.
- Carbon Monoxide Poisoning: Reduces oxygen-carrying capacity, leading to compensatory changes in red cell size.
- Benign Familial Macrocytosis: A harmless condition where individuals naturally have larger red blood cells.
Severe Macrocytosis (MCV > 125 fL)
Severely elevated MCV levels—above 125 fL—are most commonly linked to:
- Vitamin B12 or Folate Deficiencies
- Cold Agglutinin Disease
- Advanced Bone Marrow Disorders
These cases often warrant thorough evaluation to identify and address underlying health issues.
Can High MCV Be Treated?
The treatment for elevated MCV depends on the underlying cause:
-
Reversible Causes:
- Vitamin B12 or Folate Deficiency: Supplementation can effectively normalize MCV and treat the associated anemia.
- Alcoholism: Reducing alcohol intake may help improve red blood cell health.
-
Chronic or Incurable Conditions:
- For conditions like liver disease, myelodysplastic syndromes, or aplastic anemia, treatment focuses on managing symptoms and improving quality of life rather than directly reducing MCV levels.
Key Takeaways
- A high MCV is a marker of macrocytic anemia, which can result from vitamin deficiencies, chronic conditions, or lifestyle factors.
- Severe macrocytosis (MCV > 125 fL) should prompt further medical investigation to rule out serious underlying conditions.
- Early diagnosis and treatment, particularly for reversible causes like vitamin deficiencies, can significantly improve outcomes.
If you have a high MCV, consult your healthcare provider for a comprehensive evaluation to determine the cause and appropriate treatment.
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What does it mean if your Mean Corpuscular Volume (MCV) result is too low?
Low MCV: Causes and Insights into Microcytic Anemia
A low mean corpuscular volume (MCV), which measures the average size of red blood cells, is often associated with microcytic anemia. Here are the primary conditions linked to low MCV levels:
- Iron Deficiency Anemia: The most common cause of microcytic anemia, resulting from insufficient iron to produce hemoglobin.
- Thalassemia: A genetic condition where the body produces insufficient or abnormal hemoglobin. Thalassemia severity varies:
- Mild Thalassemia: May cause mild anemia or no symptoms.
- Severe Thalassemia: Requires regular red blood cell transfusions and close medical management.
- Anemia of Chronic Disease: Chronic inflammation or disease can interfere with red blood cell production, causing mild microcytosis.
- Sideroblastic Anemia: A rare disorder in which the bone marrow produces ringed sideroblasts instead of healthy red blood cells, often due to genetic or acquired causes.
- Lead Poisoning: Lead disrupts hemoglobin synthesis, leading to small, pale red blood cells.
- Hemoglobin Variants (e.g., HgC): Abnormal hemoglobin hybrids can impact red blood cell size.
- Spherocytosis: A hereditary condition where red blood cells are sphere-shaped instead of disc-shaped, leading to various hematological changes.
Severe Microcytosis (MCV < 70 fL): Key Causes
Severely low MCV levels (below 70 fL) typically indicate iron deficiency anemia or thalassemia. However, these conditions don’t always follow predictable patterns. For instance, iron deficiency anemia may occasionally present with a normal MCV.
Understanding Microcytic Anemia (MCV < 80 fL)
Microcytic anemia occurs when red blood cells are smaller than average. The leading cause is iron deficiency, which often stems from underlying conditions or lifestyle factors. Here are the most common causes of iron deficiency:
-
Blood Loss
- Gastrointestinal Bleeding: Conditions like colon cancer, peptic ulcers, or frequent use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin can cause hidden blood loss.
- Heavy Menstrual Bleeding: Excessive menstrual blood loss is a common cause of iron deficiency in premenopausal women.
-
Inadequate Dietary Iron
- Individuals following a plant-based diet or consuming an iron-poor omnivorous diet may require iron supplementation or increased intake of iron-rich foods (e.g., lean meats, legumes, fortified cereals).
-
Reduced Iron Absorption
- Medical conditions like ulcerative colitis, Crohn’s disease, or a history of weight loss surgery (e.g., gastric bypass) can impair the body’s ability to absorb iron.
- Helicobacter pylori infections can also disrupt iron absorption in the stomach.
-
Increased Iron Demand
- Pregnancy significantly raises iron requirements to support fetal development. Many pregnant individuals may need iron supplements to prevent deficiency.
Key Takeaways
- A low MCV is most commonly associated with iron deficiency anemia or thalassemia, but other conditions like chronic disease and lead poisoning can also contribute.
- Diagnosing and treating low MCV requires identifying the underlying cause, whether it’s blood loss, poor dietary intake, absorption issues, or increased demand.
- If you have a low MCV, consult your healthcare provider for appropriate testing, including iron studies, hemoglobin electrophoresis, and screening for chronic conditions.
This information is intended to help you understand potential causes and guide conversations with your healthcare provider.
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