Mean Corpuscular Volume (MCV) is a measurement included in a standard blood test called a Complete Blood Count (CBC). This value reflects the average size of your red blood cells. A high MCV indicates that your red blood cells are larger than typical. A high MCV can signal various underlying health conditions.
Understanding MCV Levels
MCV measures the average volume of red blood cells, expressed in femtoliters (fL). Red blood cells are responsible for carrying oxygen throughout the body. When MCV levels are elevated, it means these red blood cells are larger than their usual size, a condition called macrocytosis. The normal range for MCV in adults is typically 80 to 100 fL. An MCV value exceeding 100 fL is considered elevated.
Primary Causes of Elevated MCV
Elevated MCV, or macrocytosis, can stem from various factors affecting the production and development of red blood cells. One common reason involves nutritional deficiencies, particularly a lack of Vitamin B12 or folate (Vitamin B9). These vitamins are essential for DNA synthesis and proper red blood cell maturation in the bone marrow. When deficient, red blood cell division is impaired, leading to the production of larger, immature red blood cells.
Liver disease can also lead to elevated MCV levels. Liver dysfunction can alter the lipid composition of red blood cell membranes, causing them to become larger.
Chronic heavy alcohol consumption is another frequent cause of high MCV. Alcohol can directly damage the bone marrow, where red blood cells are produced, and interfere with folate metabolism. This direct toxic effect on red blood cell development results in the creation of larger red blood cells. Elevated MCV is observed in approximately 50% to 60% of individuals who chronically consume excessive alcohol quantities.
An underactive thyroid (hypothyroidism) can also be linked to macrocytosis. Hypothyroidism can impact the body’s metabolic processes, which in turn may affect red blood cell size.
Certain medications are known to cause elevated MCV as a side effect. These include some chemotherapy drugs, antiretroviral medications used for HIV treatment, and certain anticonvulsants. These drugs can interfere with red blood cell production.
Less common, but significant, causes include myelodysplastic syndromes (MDS) and hemolytic anemia. Myelodysplastic syndromes are cancers where the bone marrow fails to produce healthy blood cells, leading to abnormally large cells. In hemolytic anemia, red blood cells are prematurely destroyed, and the bone marrow releases larger, immature red blood cells (reticulocytes) to compensate, which can temporarily increase MCV.
Associated Symptoms
While a high MCV itself does not always cause symptoms, any symptoms present are typically related to the underlying condition rather than the red blood cell size directly. Fatigue and weakness are commonly reported, often due to inefficient oxygen transport by the larger red blood cells. Pale skin, shortness of breath, and dizziness can also occur, reflecting a reduced capacity of the blood to carry oxygen. Neurological symptoms such as tingling, numbness, or memory issues may arise, particularly if the high MCV is due to Vitamin B12 deficiency. Changes in appetite or unexplained weight loss might also be observed. In cases related to liver issues, jaundice, a yellowing of the skin or eyes, may be present. These symptoms can vary widely among individuals, or they may not be present at all, especially if the MCV elevation is mild.
Next Steps After a High MCV Result
Upon receiving a high MCV result, discussing it with a healthcare provider is an important next step. An abnormal MCV value alone does not provide sufficient information for a diagnosis, but it serves as an indicator that further evaluation may be needed. Your doctor will consider your complete medical history, lifestyle factors, and any symptoms you might be experiencing.
To pinpoint the underlying cause, additional diagnostic tests will likely be ordered. These may include specific blood tests to measure Vitamin B12 and folate levels. Liver function tests may be performed to assess liver health, and thyroid function tests can check for hypothyroidism. A peripheral blood smear, where a blood sample is examined under a microscope, can provide visual clues about red blood cell morphology. In rare instances, a bone marrow biopsy might be necessary, especially if a bone marrow disorder is suspected.
Treatment focuses on addressing the identified underlying cause of the elevated MCV. For nutritional deficiencies, this may involve supplements of Vitamin B12 or folate. If alcohol consumption is a factor, lifestyle changes, including reducing or stopping alcohol intake, are recommended. Medications causing the elevation may be adjusted or changed. For conditions like liver disease or thyroid disorders, management of the primary condition is important. Regular follow-up testing to monitor MCV levels and assess the effectiveness of treatment is typically part of the ongoing care.