Mean Corpuscular Volume (MCV) measures the average size of your red blood cells. This measurement is part of a Complete Blood Count (CBC), a common blood test. MCV helps healthcare providers assess red blood cell characteristics, which transport oxygen throughout your body.
Understanding MCV Levels
The MCV measures the average size of red blood cells, expressed in femtoliters (fL). For adults, the normal range is 80 to 100 fL. A value within this range indicates average-sized red blood cells. An MCV level above 100 fL is considered high, indicating larger-than-average red blood cells, a condition known as macrocytosis. Macrocytosis is an indicator that warrants further investigation, not a diagnosis itself.
Common Causes of Elevated MCV
An elevated MCV can point to several underlying health conditions. A frequent cause is a deficiency in vitamin B12 or folate (vitamin B9), both crucial for proper DNA synthesis during red blood cell production. When these vitamins are lacking, red blood cell precursors in the bone marrow have impaired DNA synthesis, leading to larger, immature cells.
Excessive alcohol consumption also frequently leads to an elevated MCV. Alcohol can directly affect the bone marrow, interfering with red blood cell development and causing nutrient deficiencies like folate. The macrocytosis caused by alcohol use reverses after abstinence.
Liver disease is another common reason for increased MCV. Impaired liver function can alter the lipid composition of red blood cell membranes, causing the cells to become larger. This mechanism is related to the severity of the liver disease.
Hypothyroidism, an underactive thyroid gland, can also be associated with elevated MCV. Low thyroid hormone levels can disrupt red blood cell production, leading to larger cells.
Certain medications can also cause an elevated MCV, such as some chemotherapy drugs (which interfere with DNA synthesis), antiretroviral therapies for HIV, and anticonvulsant drugs like phenytoin and valproic acid. Less common causes include myelodysplastic syndromes (where blood cells do not mature properly) and hemolytic anemia (where red blood cells are prematurely destroyed).
Next Steps and Medical Consultation
An elevated MCV level warrants further attention, but it is not a diagnosis on its own. It serves as an indicator that a healthcare professional should conduct additional investigation to determine the underlying cause. Self-diagnosis or self-treatment based solely on an elevated MCV is not recommended.
A doctor will likely review your medical history, including any medications you are taking, your dietary habits, and alcohol consumption. To identify the specific reason for the high MCV, additional tests may be ordered. These often include measuring vitamin B12 and folate levels, liver function tests, and thyroid function tests. A peripheral blood smear, where blood cells are examined under a microscope, can also provide valuable insights into red blood cell morphology. Consulting a healthcare professional is important to identify the cause and receive appropriate management or treatment.