Microcytosis

What is microcytosis?

Microcytosis means you have smaller-than-normal red blood cells. It’s a description, not an official diagnosis. You may learn that you have microcytosis after routine blood work, called a complete blood count (CBC). A CBC is a test that provides information about your health by assessing your blood cells.

One value on a CBC is called mean corpuscular volume (MCV). MCV is the average size of your red blood cells. For adults, microcytosis means that the MCV is less than 80 femtoliters (fL).

Microcytosis is often a sign of microcytic anemia. With microcytic anemia, red blood cells don’t have enough hemoglobin. Hemoglobin is an essential protein that allows red blood cells to transport oxygen throughout your body.

How common is microcytosis?

Microcytic anemia is the most common form of anemia in adults and children.

What are the symptoms of microcytosis?

Often, there aren’t any symptoms, and the only sign of microcytosis is a low MCV value.

When symptoms do occur, they’re the same as with microcytic anemia. They include:

• Fatigue.
• Pale skin.
• Shortness of breath.
• Rapid heartbeat.
• Pica (occurs only if the microcytosis is caused by an iron deficiency).

You may also experience symptoms associated with what’s causing microcytosis.

What causes microcytosis?

Microcytosis most often occurs when your body’s not getting enough iron. This is called iron-deficiency anemia. Iron is an essential ingredient in hemoglobin.

Environmental factors, medical conditions (inherited and acquired) and certain behaviors can also lead to microcytosis.

The most common causes of microcytosis include:

• Iron deficiency: Nutritional deficiencies can prevent you from getting enough iron in your diet. Conditions like celiac disease and H. pylori infection can prevent your body from absorbing iron, as can gastric bypass surgery. Or you may have an iron deficiency because of blood loss. Heavy menstrual bleeding and gastrointestinal (GI) bleeding are potential causes.
• Thalassemia: Thalassemia is an inherited disorder that disrupts your body’s ability to make hemoglobin. People with thalassemia may have a normal or increased number of red blood cells but low hemoglobin inside the cells (hypochromic microcytosis). Mild types of thalassemia cause microcytosis without anemia.
• Anemia of chronic disease: Long-term conditions, including autoimmune diseases, infections, kidney disease and cancer, can cause inflammation that disrupts your body’s ability to use iron to make healthy red blood cells.

Less common causes of microcytosis include:

• Rare inherited genetic conditions that interfere with the production and function of your red blood cells.
• Mineral deficiencies (copper).
• Lead poisoning.

How is microcytosis diagnosed?

Microcytosis isn’t an official diagnosis. Instead, it’s a medical term that describes smaller-than-normal red blood cells.

Your healthcare provider will consider your symptoms, factors like your age and sex and your medical history to determine likely causes. For example, iron-deficiency anemia is a likely cause if you get heavy periods. If you have a family history of thalassemia, this may be the cause.

Your healthcare provider can run tests to determine the cause.

What tests will be done to determine what’s causing microcytosis?

Tests and values include:

• Peripheral blood smear: A healthcare provider views your blood cells under a microscope. The blood smear can help confirm that your red blood cells are small and identify other abnormalities. Various sizes and abnormal shapes (poikilocytosis) can suggest certain conditions that cause microcytosis.
• Red cell distribution width (RDW):RDW measures variation in your red blood cells’ size. It’s a value included in a CBC. Red blood cells are usually the same size. Lots of variety in cell sizes (anisocytosis) can suggest certain conditions.
• Iron levels: Decreased iron levels are a sign of iron-deficiency anemia.
• Ferritin levels: Ferritin is a protein inside your cells that stores iron. Ferritin levels are useful in determining how much iron is available for use in your body.
• Total iron binding capacity (TIBC): In combination with the iron and ferritin levels, this test helps in the diagnosis of iron deficiency. These levels also help in identifying anemia of chronic disease or inflammation.

Once your provider rules out an iron deficiency, you’ll need other tests to confirm thalassemia as the cause, including hemoglobin electrophoresis, plus genetic tests.

How is microcytosis treated?

Treatment depends on what’s causing your small red blood cells. You may not need treatment if you’re not experiencing symptoms and your test results aren’t concerning.

Depending on the cause, treatments may include dietary changes, iron supplements (for iron deficiency anemia) or a blood transfusion if the anemia is very severe. Follow your healthcare provider’s treatment plan based on the underlying issue.

Is microcytosis reversible?

It depends on the cause. Often, treating the underlying issue reverses microcytosis. Your healthcare provider can advise you on how treatment will impact your blood cells and overall health.

How can I reduce my risk of having microcytosis?

You can’t prevent all conditions that can lead to small red blood cells, but you can put healthy habits into place to reduce your risk. This includes ensuring that you get enough iron in your diet. Iron-rich foods include tuna, tofu, peas, beans, and many fruits and vegetables. Also, if you have a condition that limits your ability to absorb iron from your diet, including gastric bypass surgery, talk to your healthcare provider about what iron supplements you might need.

Follow your healthcare provider’s guidance about reducing your risk of anemia if you have a condition that puts you at risk, like thalassemia or an autoimmune disease.

What happens if microcytosis is left untreated?

Not everyone with microcytosis or microcytic anemia needs treatment. If you have a serious underlying condition causing your small red blood cells, it’s important to get diagnosed and treated as soon as possible. Follow your healthcare provider’s guidance about when you need treatment and what outcomes to expect.

Is microcytosis serious?

Microcytosis is just a characteristic of your red blood cells. It may be one sign (among others) that you have a condition that requires treatment. Often, it’s a harmless finding.

Your healthcare provider will let you know if your microcytosis signals a condition that requires treatment.

What questions should I ask my doctor?

Follow your provider’s guidance about what comes next if you learn you have microcytosis. Questions might include:

• Should I be concerned about my low MCV?
• What tests will I need to determine what’s causing microcytosis?
• Will I need treatment?
• What outcomes should I expect from treatment?
• Are there lifestyle changes I can make to reverse my microcytosis?

Is microcytosis cancerous?

Microcytosis may be a sign of cancer, but it’s usually a sign of other conditions. Most often, microcytosis is a sign of an iron deficiency. It’s important not to assume cancer (or any other condition) until your healthcare provider explains what your bloodwork results mean for your health.

A note from Cleveland Clinic

It can be alarming to learn of any abnormal results on a medical test. But abnormal ranges don’t always mean you’re sick or need treatment. Instead, values like MCV provide just one bit of information that allows your healthcare provider to understand your overall health. Look to them for guidance on how your test results affect your care moving forward.