A high Mean Corpuscular Volume (MCV) blood test result can be a source of concern, but it does not automatically indicate cancer. While an elevated MCV can be associated with various health conditions, it serves as a piece of a larger diagnostic puzzle, guiding further investigation into your overall health.
What is MCV and High MCV?
MCV, or Mean Corpuscular Volume, is a measurement that determines the average size of your red blood cells (RBCs). This measurement is typically included as part of a routine Complete Blood Count (CBC), a common blood test that evaluates different types of cells in your blood. Red blood cells are responsible for transporting oxygen from your lungs to every cell in your body, and their size can provide information about their ability to carry oxygen effectively.
A “high MCV” result, also known as macrocytosis, indicates that your red blood cells are larger than their typical size. For adults, the normal MCV range generally falls between 80 and 100 femtoliters (fL); an MCV value exceeding 100 fL is considered high. While a high MCV on its own may not cause symptoms, it can sometimes be associated with anemia, a condition where the body lacks enough healthy red blood cells.
Common Causes of Elevated MCV
Elevated MCV most frequently stems from non-cancerous conditions, offering a broader context for understanding such results. One of the most common reasons for macrocytosis is a deficiency in vitamin B12 or folate (vitamin B9). These vitamins are necessary for proper DNA synthesis and cell division in the bone marrow, where red blood cells are produced. When these nutrients are insufficient, red blood cells grow larger than normal because they cannot divide properly, leading to macrocytic anemia.
Excessive alcohol consumption is another common cause of elevated MCV. Chronic alcohol intake can directly damage bone marrow and interfere with folate metabolism, resulting in the production of larger red blood cells. The MCV elevation from alcohol appears after several weeks of heavy drinking. Liver disease, regardless of alcohol involvement, can also lead to macrocytosis due to changes in lipid metabolism that affect red blood cell membranes, increasing their surface area.
Hypothyroidism, an underactive thyroid gland, has also been linked to elevated MCV. Low thyroid hormone levels can disrupt the normal production and maturation of red blood cells in the bone marrow. Certain medications can also cause macrocytosis by interfering with folate or vitamin B12 metabolism or by directly affecting bone marrow function, including antiretroviral agents, anticonvulsants, and some chemotherapy drugs.
High MCV and Cancer
While a high MCV is often linked to more common causes like vitamin deficiencies or alcohol use, it can sometimes be associated with certain types of cancer. Myelodysplastic syndromes (MDS) are a group of cancers that affect blood cells in the bone marrow, where immature blood cells become abnormal and struggle to develop into mature, healthy cells. This can lead to a high MCV, as the bone marrow produces fewer but larger, dysfunctional red blood cells.
Some leukemias and lymphomas may also present with higher-than-normal MCV readings. Cancers that cause nutrient deficiencies, such as gastrointestinal cancers leading to malabsorption of B12 or folate, can indirectly result in elevated MCV. A high MCV is rarely the sole indicator of cancer and is often accompanied by other specific symptoms or abnormal blood markers that prompt further investigation.
What to Do After a High MCV Result
Receiving a high MCV result can be unsettling, but consult with a healthcare provider for proper interpretation. Your doctor will consider your full medical history, any symptoms you may be experiencing, and the results of other blood tests to understand the overall picture. A high MCV alone does not provide enough information for a diagnosis.
Further diagnostic tests are often necessary to pinpoint the underlying cause. These may include specific vitamin B12 and folate level tests, liver function tests, and a thyroid panel to check for hypothyroidism. A reticulocyte count, which measures immature red blood cells, and a peripheral blood smear, where blood cells are examined under a microscope, can also provide valuable clues. If more serious conditions like myelodysplastic syndromes are suspected, a bone marrow biopsy may be performed to examine the bone marrow’s cellular composition and function directly. Self-diagnosis is not recommended; professional medical advice is needed for an accurate diagnosis and appropriate management plan.