Low MCV: What It Means & What to Do

Low MCV can indicate certain health problems such as iron deficiency anemia, thalassemia, sideroblastic anemia, or lead poisoning.

MCV, or mean corpuscular volume, is considered low in adults when it measures below 83 fL on a complete blood count (CBC). This result shows microcytosis, which means that the red blood cells are smaller than normal.

When MCV is low, it’s important to see a primary care doctor (or a pediatrician for children) to determine the cause and begin the right treatment. Depending on the diagnosis, treatment may involve medications, supplements, or, in some cases, blood transfusions.

Possible causes

Low MCV (microcytosis) may be associated with the following conditions:

1. Iron deficiency anemia

Iron deficiency anemia is the most common cause of low MCV. It can cause symptoms such as fatigue, drowsiness, pale skin, and trouble concentrating.

This condition occurs when the body doesn’t have enough iron to form the heme portion of hemoglobin, which transports oxygen in the blood.

What to do: If anemia is suspected, it’s recommended to see a primary care provider for proper evaluation and treatment. Your provider may prescribe iron supplements and advise eating iron-rich foods like lentils, parsley, beans, and red meat.

2. Thalassemia

Low MCV can also indicate a thalassemia, which is a genetic form of anemia characterized by reduced production of healthy red blood cells and hemoglobin.

Symptoms may include pale skin, fatigue, weakened immunity, slow growth, and in severe cases, enlargement of the spleen and liver.

What to do: If a thalassemia is confirmed, treatment may involve iron-chelating medications, folic acid supplements, and in some cases, regular blood transfusions every few weeks.

3. Sideroblastic anemia

Sideroblastic anemia is another condition that can cause low MCV. It happens when the body can’t properly use iron to make hemoglobin, leading to iron buildup inside the mitochondria of immature red blood cells (erythroblasts).

What to do: If sideroblastic anemia is suspected, a primary care doctor or hematologist should be consulted for diagnosis and treatment. Management may include supplements with vitamin B6 (pyridoxine), copper, or folic acid, along with limiting alcohol consumption.

In severe cases, especially when bone marrow function is affected, a bone marrow transplant may be recommended.

4. Anemia of chronic disease

Low MCV can also be linked to anemia of chronic disease, which occurs when long-term health conditions interfere with red blood cell production. This results in a reduced number of red blood cells and lower hemoglobin levels.

What to do: If anemia of chronic disease is diagnosed, the doctor may recommend erythropoietin injections, a hormone that stimulates red blood cell production. Iron supplementation may also be prescribed depending on blood test results, including serum iron and transferrin levels.

5. Lead poisoning

Lead poisoning can cause low MCV because this metal interferes with the formation of heme and hemoglobin, resulting in smaller red blood cells.

Symptoms may include headaches, memory problems, weakness, and encephalopathy.

What to do: Lead poisoning is a medical emergency. If it’s suspected, go to the nearest emergency department or call emergency services (911 in the US). Treatment may include chelation therapy using FDA-approved agents such as succimer (DMSA) or edetatecalcium disodium (EDTA).

Low MCV and low MCH

When both MCV and MCH (mean corpuscular hemoglobin) are low, this often indicates microcytic anemia, such as iron deficiency anemia, thalassemia, or sideroblastic anemia.

Low MCV and MCH with high RDW

When MCV and MCH are low but RDW (red cell distribution width) is high, this can indicate conditions such as microcytic anemia, megaloblastic anemia, or liver and kidney problems.

Low MCV in children

As in adults, low MCV in children can be caused by iron deficiency anemia, thalassemia, sideroblastic anemia, chronic disease, or lead poisoning.

In children aged 6 to 12 years, MCV is considered low when it’s below 77 fL. In children aged 2 to 6 years, it’s considered low when it’s below 75 fL.

MCV blood test

To determine whether MCV is low, it’s recommended to see a primary care provider, who can order a complete blood count (CBC).