Mean corpuscular volume (MCV) measures the size of your red blood cells. It can be used to help diagnose blood disorders. Keep reading to learn more about the causes and health effects of low and high MCV.

What is MCV?

Mean corpuscular volume (MCV) is the average size (volume) of the red blood cells in your body. It is normally measured as part of a complete blood count, which measures your hemoglobin, hematocrit, and red blood cell levels [1].

Along with the red cell distribution width (RDW) test, MCV is used to diagnose many diseases, including anemia, thalassemia, liver disease, and iron deficiency [1].

MCV Normal Range

The normal range for MCV is 80 – 94 fl [1].

Low MCV

An MCV below normal means that your red blood cells are smaller than normal (microcytic). Microcytosis is a result of the inability to form hemoglobin, which is a protein that is responsible for transporting oxygen in the blood [1, 2].

Microcytosis patients usually do not show any symptoms, unless their anemia is severe. Other complete blood count tests can help determine the cause of microcytosis, such as RDW and iron markers [3].

The four main causes of microcytosis are iron deficiency, anemia of chronic disease, thalassemic conditions, and sideroblastic anemia [2].

Causes of Low MCV

1) Iron Deficiency

The most common cause of low MCV is iron deficiency. Without enough iron in the body, red blood cells cannot make hemoglobin, and this results in a smaller red blood cell size [2, 4].

In a study of 466 patients, the main cause of their microcytosis was iron deficiency. Their MCV also correlated with iron deficiency severity [5].

Rheumatoid arthritis and lead poisoning can also cause iron deficiency and decrease MCV [6, 7, 8].

2) Anemia

Anemia, often resulting from an iron deficiency or chronic disease, can cause low MCV [4].

3) Thalassemia

Thalassemia is an inherited disorder in which the body makes a low amount or abnormal form of hemoglobin. Decreased hemoglobin levels cause red blood cells to decrease in size, resulting in a low MCV [9].

4) Copper Deficiency

Copper deficiency may cause low MCV. However, it can also cause normal or high MCV [10].

Ways to Increase MCV

Make sure you are eating a healthy and nutritious diet. In order to prevent nutrient deficiency, it is important that your diet consists of the recommended amount of iron and copper [2, 4, 10].

If you are iron-deficient, eat more iron-rich foods include liver, meat, fish, and eggs [11, 12].

If you have copper deficiency, eat more copper-rich foods, such as liver, seafood (shrimp), and dark leafy vegetables [13].

High MCV

Your mean corpuscular volume (MCV) is above normal. This means that your red blood cells are bigger than normal (macrocytic) [1].

By itself, macrocytosis does not cause any symptoms. However, the diagnosis of macrocytosis can help provide information about any underlying health conditions [14].

Causes of High MCV

1) Anemia

One common cause of high MCV is anemia, particularly the kinds that result from deficiencies of vitamin B12 and folate (vitamin B9), such as megaloblastic anemia. Aplastic anemia also results in high MCV [15, 16, 17].

With megaloblastic anemia, red blood cells are larger, but their core (nucleus) is smaller. These abnormalities are due to impaired DNA synthesis, which can result from folate and B12 deficiency. The effects are most apparent in rapidly dividing cells such as blood cells and gut cells.

HIV infections can also cause high MCV as a result of the infection impairing DNA synthesis.

2) Alcohol Intake and Alcoholism

Alcohol intake is one of the most common causes of high MCV. Alcoholics have higher MCV than non-alcoholics. In one study, after alcoholic-liver disease patients abstained from drinking alcohol, their MCV decreased significantly [18, 19, 20].

3) Other Disorders

  • Acute leukemia [21]
  • Reticulocytosis (increased red blood cell production) [22]
  • Liver disease [20, 19]
  • Hypothyroidism (underactive thyroid gland) [23]

4) Drugs

  • Chemotherapy drugs [14, 24]
  • Antiretrovirals [25, 14]
  • Diuretics [14, 26]
  • Antimicrobials [14, 26]
  • Anticonvulsants [14]

Health Effects of Having a High MCV

1) High MCV is Associated with Poor Brain Function

In older adults, a large MCV is associated with reduced brain (cognitive) function. Larger red blood cells have problems with movement and transporting oxygen to the brain. In a study of 827 seniors, people with high MCV had problems with attention and memory [27].

2) High MCV Increases Tumor Risk

People with high MCV have an increased risk of tumors. Men with high MCV have increased risk of esophageal squamous cell carcinoma, while women have increased risk for colorectal adenoma [28, 29].

3) High MCV Increases Mortality Risk in Patients

Chronic kidney disease and heart failure patients with a high MCV have a higher risk of death. Higher MCV increased the risk of dying from all-causes [30, 31].

Ways to Decrease MCV

Diet

If you have megaloblastic anemia, you should increase your dietary intake of foods that are rich in vitamin B12 and folate (vitamin B9). Folate can be found in leafy green vegetables, while vitamin B12 is abundant in meat products including chicken, turkey, lamb, beef, and pork liver, and dairy products such as yogurt and milk [32, 33, R].

Lifestyle Changes

Reducing your alcohol intake can also prevent your MCV from becoming too high. Alcoholics who refrain from drinking alcohol have significant decreases in MCV [18, 19, 20].

Consult your doctor about the medications that you are taking to check if any of them might be affecting your MCV, and to see if there are any safe alternatives that you can take instead [14, 24, 25].

Supplements

If you are deficient in vitamin B12 or folate, taking supplements can increase your vitamin levels. It can also help with deficiency-induced megaloblastic anemia [15, 34].

Irregular MCV Levels?

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