Microcytosis is a term used to describe red blood cells that are smaller than normal. Anemia is when you have low numbers of properly functioning red blood cells in your body. In microcytic anemias, your body has fewer red blood cells than normal. The red blood cells it does have are also too small. Several different types of anemias can be described as microcytic.

Microcytic anemias are caused by conditions that prevent your body from producing enough hemoglobin. Hemoglobin is a component of your blood. It helps transport oxygen to your tissues and gives your red blood cells their red color.

Iron deficiency causes most microcytic anemias. Your body needs iron to produce hemoglobin. But other conditions can cause microcytic anemias, too. To treat a microcytic anemia, your doctor will first diagnose the underlying cause.

You may not notice any symptoms of microcytic anemia at first. Symptoms often appear at an advanced stage when the lack of normal red blood cells is affecting your tissues.

Common symptoms of microcytic anemias include:

• fatigue, weakness, and tiredness
• loss of stamina
• shortness of breath
• dizziness
• pale skin

If you experience any of these symptoms and they don’t resolve within two weeks, make an appointment to see your doctor.

You should make an appointment to see your doctor as soon as possible if you experience severe dizziness or shortness of breath.

Microcytic anemias can be further described according to the amount of hemoglobin in the red blood cells. They can be either hypochromic, normochromic, or hyperchromic:

1. Hypochromic microcytic anemias

Hypochromic means that the red blood cells have less hemoglobin than normal. Low levels of hemoglobin in your red blood cells leads to appear paler in color. In microcytic hypochromic anemia, your body has low levels of red blood cells that are both smaller and paler than normal.

Most microcytic anemias are hypochromic. Hypochromic microcytic anemias include:

Iron deficiency anemia: The most common cause of microcytic anemia is an iron deficiency in the blood. Iron deficiency anemia can be caused by:

• inadequate iron intake, usually as a result of your diet
• being unable to absorb iron due to conditions like celiac disease or Helicobacter pyloriinfection
• chronic blood loss due to frequent or heavy periods in women or by gastrointestinal (GI) bleeds from upper GI ulcers or irritable bowel syndrome
• pregnancy

Thalassemia: Thalassemia is a type of anemia that’s caused by an inherited abnormality. It involves mutations in the genes needed for normal hemoglobin production.

Sideroblastic anemia: Sideroblastic anemia can be inherited due to gene mutations (congenital). It can also be caused by a condition acquired later in life that impedes your body’s ability to integrate iron into one of the components needed to make hemoglobin. This results in a buildup of iron in your red blood cells. Congenital sideroblastic anemia is usually microcytic and hypochromic.

2. Normochromic microcytic anemias

Normochromic means that your red blood cells have a normal amount of hemoglobin, and the hue of red is not too pale or deep in color. An example of a normochromic microcytic anemia is:

Anemia of inflammation and chronic disease: Anemia due to these conditions is usually normochromic and normocytic (red blood cells are normal in size). Normochromic microcytic anemia may be seen in people with:

• infectious diseases, such as tuberculosis, HIV/AIDS, or endocarditis
• inflammatory diseases, such as rheumatoid arthritis, Crohn’s disease, or diabetes mellitus
• kidney disease
• cancer

These conditions can prevent red blood cells from functioning normally. This can lead to decreased iron absorption or utilization.

3. Hyperchromic microcytic anemias

Hyperchromic means that the red blood cells have more hemoglobin than normal. High levels of hemoglobin in your red blood cells makes them a deeper hue of red than normal.

Congenital spherocytic anemia: Hyperchromic microcytic anemias are rare. They may be caused by a genetic condition known as congenital spherocytic anemia. This is also called hereditary spherocytosis. In this disorder, the membrane of your red blood cells doesn’t form correctly. This causes them to be rigid and improperly spherical shaped. They are sent to be broken down and die in the spleen because they don’t travel in the blood cells properly.

4. Other causes of microcytic anemia

Other causes of microcytic anemia include:

• lead toxicity
• copper deficiency
• zinc excess, which causes copper deficiency
• alcohol use
• drug use

Microcytic anemias are often first spotted after your doctor has ordered a blood test known as a complete blood count (CBC) for another reason. If your CBC indicates that you have anemia, your doctor will order another test known as a peripheral blood smear. This test can help spot early microcytic or macrocytic changes to your red blood cells. Hypochromia, normochromia, or hyperchromia can also be seen with the peripheral blood smear test.

Your primary care doctor may refer you to a hematologist. A hematologist is a specialist who works with blood disorders. They may be able to best diagnose and treat the specific type of microcytic anemia and identify its underlying cause.

Once a doctor has diagnosed you with microcytic anemia, they will run tests to determine the cause of the condition. They may run blood tests to check for celiac disease. They may test your blood and stool for H. pylori bacterial infection.

Your doctor might ask you about other symptoms you’ve experienced if they suspect that chronic blood loss is the cause of your microcytic anemia. They may refer you to a gastroenterologist if you have stomach or other abdominal pain. A gastroenterologist might run imaging tests to look for different conditions. These tests include:

• abdominal ultrasound
• upper GI endoscopy (EGD)
• CT scan of the abdomen

For women with pelvic pain and heavy periods, a gynecologist may look for uterine fibroids or other conditions that could cause heavier flows.

Treatment for microcytic anemia focuses on treating the underlying cause of the condition.

Your doctor may recommend that you take iron and vitamin C supplements. The iron will help treat the anemia while the vitamin C will help increase your body’s ability to absorb the iron.

Your doctor will focus on diagnosing and treating the cause of the blood loss if acute or chronic blood loss is causing or contributing to microcytic anemia. Women with iron deficiency from severe periods may be prescribed hormonal therapy, such as birth control pills.

In cases of microcytic anemia so severe that you’re at risk for complications like cardiac failure, you may need to get a blood transfusion of donor red blood cells. This can increase the number of healthy red blood cells that your organs need.

Treatment can be relatively straightforward if simple nutrient deficiencies are the cause of microcytic anemia. As long as the underlying cause of the anemia can be treated, the anemia itself can be treated and even cured.

In very severe cases, untreated microcytic anemia can become dangerous. It can cause tissue hypoxia. This is when the tissue is deprived of oxygen. It can cause complications including:

• low blood pressure, also called hypotension
• coronary artery problems
• pulmonary problems
• shock

These complications are more common in older adults who already have pulmonary or cardiovascular diseases.

The best way to prevent microcytic anemia is to get enough iron in your diet. Increasing your vitamin C intake can also help your body absorb more iron. You can also consider taking a daily iron supplement. These are often recommended if you already have anemia. You should always talk to your doctor before you start taking any supplements.

You can also try to get more nutrients through your food.

Foods rich in iron include:

• red meat like beef
• poultry
• dark leafy greens
• beans
• dried fruits like raisins and apricots

Foods rich in vitamin C include:

• citrus fruits, especially oranges and grapefruits
• kale
• red peppers
• Brussels sprouts
• strawberries
• broccoli