A complete blood count (CBC) is a routine blood test that measures various components of your blood, including red blood cells, white blood cells, and platelets. The Mean Corpuscular Volume (MCV) is a specific measurement in a CBC. This value provides information about the average size of your red blood cells. Understanding what a high MCV result signifies and when it might indicate a health concern is important for individuals reviewing their lab results.
What MCV Means on Your Blood Test
The MCV measurement indicates the average size of your red blood cells. Red blood cells are responsible for carrying oxygen throughout your body, and their size can impact their efficiency. A normal MCV falls within a range of 80 to 100 femtoliters (fL).
When your blood test shows a high MCV, it means your red blood cells are larger than this average size. This condition is medically referred to as macrocytosis. A high MCV suggests that the body is producing red blood cells that are abnormally large.
Why Your MCV Might Be High
Numerous factors can contribute to an elevated MCV, ranging from common nutritional issues to underlying medical conditions. One of the most common reasons for macrocytosis is a deficiency in certain vitamins. Both vitamin B12 and folate (vitamin B9) are essential for the proper synthesis of DNA and the normal division of red blood cells during their production in the bone marrow. A lack of these vitamins can hinder proper cell division, leading to the formation of fewer, but larger, immature red blood cells.
Excessive alcohol consumption is another frequent cause of high MCV. Alcohol can interfere with nutrient absorption, particularly folate, and can also directly affect bone marrow function, leading to the production of larger red blood cells. Liver disease can also elevate MCV because the liver plays a role in red blood cell metabolism and nutrient storage. Certain medications, such as those used in chemotherapy or some antiviral drugs, can also impact red blood cell size as a side effect.
Less common causes of a high MCV include an underactive thyroid, also known as hypothyroidism, which can affect blood cell production. Bone marrow disorders, such as myelodysplastic syndromes, involve problems with the production of blood cells in the bone marrow and can lead to macrocytosis. Additionally, some types of hemolytic anemia, where red blood cells are prematurely destroyed, can also result in a higher MCV as the body tries to compensate by releasing larger, immature cells.
Understanding When High MCV Needs Attention
An elevated MCV value, particularly if it’s an isolated finding without accompanying symptoms, may not always indicate an immediate serious health concern. However, any abnormal blood test result, including a high MCV, warrants a discussion with a healthcare professional for proper evaluation. The presence of certain symptoms alongside a high MCV can suggest a need for more prompt medical attention.
If you experience persistent fatigue, unexplained weakness, or shortness of breath, these symptoms, combined with a high MCV, could signal an underlying issue like anemia. Other symptoms that warrant evaluation include:
- Pale or yellowish skin
- Tingling or numbness in the hands and feet, which can be linked to vitamin B12 deficiency
- Difficulty concentrating or irritability
- Unexplained weight loss
- Easy bruising or bleeding
- Jaundice (yellowing of the skin or eyes)
The degree to which your MCV is elevated, along with any other abnormal values in your complete blood count, will guide your doctor’s assessment of the situation.
Next Steps After a High MCV Result
Upon receiving a high MCV result, schedule a consultation with your doctor. They will review your complete medical history, including any medications you are currently taking, and perform a physical examination to look for any signs or symptoms related to your MCV elevation. This comprehensive approach helps in understanding your overall health context.
Your doctor will likely order additional blood tests to help pinpoint the specific cause of the high MCV. These tests often include:
- Measurements of vitamin B12 and folate levels to check for nutritional deficiencies
- Liver function tests to assess liver health
- Thyroid function tests to help rule out hypothyroidism
- A reticulocyte count, which measures young red blood cells, to indicate if the bone marrow is producing new cells at an increased rate
- A bone marrow biopsy, if more serious bone marrow conditions are suspected, to directly examine the cells
The specific treatment approach will be determined by the identified underlying cause, with many causes being manageable or treatable.