A high mean corpuscular volume, or MCV, indicates that a person's red blood cells have a larger average size than normal. An MCV level that is above average is called macrocytosis.
Mean corpuscular volume (MCV) is a test that shows the average volume of an individual's red blood cells. A normal MCV level falls between 80 and 96 femtoliters. A high MCV level is considered a number of 100 femtoliters or more. If an individual also has a low blood cell count, doctors can make the diagnosis of macrocytic anemia. Macrocytic anemia can arise from certain conditions, such as a deficiency in vitamin B12 or folic acid. Some blood cancers can cause macrocytic anemia, as can heavy alcohol use. Certain medications can produce side effects that trigger a high MCV reading. Macrocytic anemia can also exist in healthy individuals who are replenishing their blood supplies after surgery.
Red Blood Cells
Red blood cells play an important role in health. They help deliver oxygen to cells throughout the body and bring carbon dioxide back to the lungs for expulsion. Oxygen delivery is accomplished through hemoglobin, which is a protein found inside red blood cells. Red blood cells are produced in the bone marrow. They have a relatively short lifespan of 120 days before dying. Problems with a person's red blood cells can arise from several conditions. Various illnesses and infections can cause red cell disorders, as can inherited or genetic diseases. Dietary problems, such as vitamin deficiency, can also interfere with red blood cell performance.
The MCV Test
Doctors might discover that a patient has a high MCV level during a routine examination. They might also suggest an MCV test if a patient complains of symptoms associated with anemia or oxygen-poor blood. Symptoms that might indicate anemia include fatigue, irregular heartbeat, cold hands and feet, and pale skin. In some cases, heart failure produces abnormal blood cell readings. Doctors might also suspect that children have oxygen-deprived blood when they develop more slowly than others their age.
Through the MCV, which is usually accompanied by a complete blood count (CBC) test, doctors can determine the underlying cause of the problem. Anemia caused by a vitamin B12 or folate deficiency is one potential explanation for high MCV levels. Other possible conditions that raise MCV levels are myelodysplasia, hyperthyroidism (an overactive thyroid) and certain types of liver disease. Doctors might order more tests to identify the specific type of anemia that a person has or to get a complete overview of the individual's blood health.
Iron-deficient anemia means that a person's iron levels are so low that he or she cannot produce enough red blood cells. This is the most common type of anemia. It can result from major blood loss, an inability to absorb iron in foods and a diet that does not have enough iron. Women may also get iron-deficient anemia from heavy menstrual cycles. Other types of anemia are sickle-cell anemia, which is an inherited disease; normocytic anemia, which means that a person's body does not produce enough red blood cells; hemolytic anemia, where the body cannot produce enough red blood cells to meet its needs; and Fanconi anemia, which is another type of anemia that can be inherited.