Microcytic Anemia: Symptoms, Causes, Treatment, And Types

Anemia is any condition in which red blood cells cannot carry enough oxygen to supply the body’s tissues. It comes in several types and is often (but not always) associated with iron deficiency.

One type of anemia is microcytic anemia.

What is microcytic anemia?

Microcytic anemia is a form of anemia that is characterized by smaller-than-normal red blood cells. These small blood cells are less functional and carry less oxygen in your blood. It is also called microcytosis.

Microcytic vs. macrocytic anemia

Microcytic anemia stands in contrast to macrocytic anemia, which is characterized by larger-than-normal red blood cells which also do not function correctly. It is also called macrocytosis.

The similarity in the technical terms can sometimes cause confusion, especially as both are types of anemia and end up causing similar problems. However, they have very different causes.

Symptoms of microcytic anemia

In many cases, people with microcytosis have no symptoms. The condition is often found when you need a complete blood count for some other reason.

However, microcytic anemia is associated with iron deficiency anemia, which can cause the following symptoms:

• Lack of energy

• Shortness of breath

• Heart palpitations

• Pale complexion

Rarer symptoms include:

• Headaches

• Tinnitus

• Altered sense of taste

• Itchiness

• Sore or abnormally smooth tongue

• Pica or craving for non-food items such as ice, paper, or clay

• Hair loss

• Difficulty swallowing

• Ulcers on the corners of the mouth

• Spoon-shaped nails

Most people only have some of these symptoms, and anemia is typically diagnosed through a blood test.

What causes microcytic anemia

Microcytic anemia is typically split into three subtypes with different causes.

Hypochromic microcytic anemia

In this form of anemia, the cells are small and also lighter than normal in color. Depleted iron reserves most often cause this form of anemia. Root causes include insufficient iron consumption, gut problems resulting in poor absorption, acute or chronic blood loss (such as from ulcers), or increased demand for iron. The latter is often associated with recovery from major trauma or surgery, but microcytosis is also known during pregnancy.

It is also a symptom of some hereditary anemia caused by the inability to absorb iron properly, resulting in low hemoglobin in the blood. 

Hypochromic microcytic anemia is also often associated with iron overload, where the iron that is not used accumulates in the liver, causing impaired function. This form of anemia is typically diagnosed in childhood.

Normochromic microcytic anemia

This means the cells are small but normal in color, having a normal amount of hemoglobin. This is most often found in people with certain diseases, which include HIV, endocarditis, rheumatoid arthritis, Crohn's disease, diabetes, kidney disease, and cancer. Because of this, it is more often found in older individuals.

Hyperchromic microcytic anemia

In hyperchromic microcytic anemia, the red blood cells have too much hemoglobin, resulting in a darker color. It is extremely rare and is caused by a condition known as hereditary spherocytosis. This condition also causes jaundice, an enlarged spleen, and an elevated risk of gallstones. 

Severe hereditary spherocytosis can result in life-threatening anemia and can delay sexual development and reduce stature. However, many people with the condition have very mild anemia or no symptoms.

Other causes

Microcytic anemia can also be caused by thalassemia, an inherited blood disorder that affects your ability to produce normal hemoglobin. 

Thalassemia is more common in people from the Mediterranean, Asia, Africa, and the Middle East. Sideroblastic anemia, which results from abnormal utilization of iron in your blood marrow, can also cause microcytosis.¹

Microcytic anemia can be a symptom of lead poisoning. Lead poisoning is less common than it used to be and is mostly caused by direct or indirect occupational exposure. Some other causes include too little copper, too much zinc, or excessive use of alcohol and drugs.

How microcytic anemia is diagnosed

Microcytic anemia is most often diagnosed after a complete blood count is taken, often for other reasons. A CBC includes counting the number of red blood cells in a sample to see if there are too few, a classic sign of anemia. However, doctors also typically look at red blood cells under a microscope to assess their health and color.

The presence of asymptomatic anemia is more common than other diseases in complete blood counts, which are usually taken as part of an overall health check.

If you have a complete blood count done and you menstruate, make sure your doctor knows where in your cycle you are, as menstruation typically affects red blood cell counts.

If you have symptoms of anemia, such as pallor or lethargy, then your doctor may order a CBC to check for anemia. A CBC also assesses your white cell count; a low count may indicate autoimmunity or cancer, while a high one can indicate a hidden infection or a reaction to some medication you might be taking. This can be important information to assess the cause of your anemia.

Once a CBC indicates anemia, you may be referred to a hematologist, or blood specialist, to help diagnose and treat the specific type of microcytic anemia you have. They will also run blood tests to check for celiac disease, test your blood and stool for certain infections, or do imaging tests to look for a bleeding ulcer or other potential cause of chronic blood loss. You may be referred to a gynecologist if you also have unusually heavy periods or pelvic pain.

Treatment 

The majority of cases of microcytic anemia are caused by iron deficiency. If you have severe anemia symptoms or issues with your gut, your doctor may recommend an iron infusion. This means you receive iron supplementation by IV in a hospital. However, for most people, the treatment is oral iron supplementation. Vitamin C supplements may be added to help your body absorb iron better.

Your doctor may also refer you to a nutritionist to discuss long-term diet changes to increase your iron intake. 

Menstruation and pregnancy may both require iron supplementation.

Iron-rich foods include dark-green leafy vegetables, brown rice, legumes, beans, nuts, seeds, meat, fish, tofu, eggs, and dried fruit. Some cereals are also fortified with iron. 

If you are vegetarian or vegan, you are more likely to have anemia because these diets contain less iron, and iron from plant sources is less bioavailable (harder to absorb).²

Vegetarians and vegans need to take special care to consume enough iron. Those who rely on plant sources of iron should consume 1.8 times the amount of iron recommended for those who get it from animal sources. Vegan iron supplements are also available.

In some cases, your anemia might be caused by an underlying condition. In this case, treating the underlying condition is important, not just increasing iron intake. 

For example, if your anemia is caused by failure to absorb iron in the gut as a result of inflammatory bowel disease, then the goal of treatment is to resolve that by, for example, the use of immunomodulators or corticosteroids. 

If you have thalassemia, you may need blood transfusions, depending on the severity of your condition. If an infectious disease causes your anemia, then the disease will have to be treated. Most people with HIV can avoid anemia by complying with their medication and treatment protocols.

In severe anemia, where your life might be in danger, you may have to receive a blood transfusion.

Do not increase iron if you have symptoms of anemia without talking to your doctor first. In some cases, you may be experiencing hemochromatosis, otherwise known as iron overload. The iron that is not being properly used by your blood is accumulating in your organs.

Increasing iron intake without addressing the cause of the overload can cause significant issues. You will need medication to remove the iron from your liver.

Prevention

The best way to prevent microcytic anemia is to get enough iron in your diet. If you are vegetarian or vegan, you need to be particularly careful about your iron intake, as you are avoiding the best source, which is red meat and/or liver.

You may also want to increase iron intake if you are pregnant or trying to get pregnant. When pregnant, you share your blood supply with the fetus and need to make more hemoglobin, which requires more iron. Not getting enough iron can affect both you and the baby. 

Menstruating women also need more iron as they are losing blood. If you regularly experience mild anemia after periods and are not trying to get pregnant, consider going on oral contraceptives, which reduce heavy flow and blood loss. You should discuss this with your doctor.

Getting enough vitamin C also helps in the prevention of anemia. Vitamin C deficiency can aggravate anemia by making it hard to absorb enough iron. You can take a supplement or increase your intake of fruits and vegetables.

Some doctors suggest increasing iron if you have symptoms of sluggishness and fatigue, as you may have very mild anemia, and addressing it can increase energy levels and mood.³

Always tell your doctor if you are taking iron supplements (or any other supplements).

You can also prevent anemia by being proactive about getting medical treatment for conditions, such as stomach ulcers, that can cause it. However, the best thing you can do to keep from developing any form of anemia is to eat enough iron.

There is no way to prevent hereditary conditions that cause anemia. Genetic counseling can help you determine if your future children may be at risk for one of these conditions and can help you make an educated decision about whether to have biological children if, for example, thalassemia runs in your family.

The lowdown

Microcytic anemia is a form of anemia in which your body produces red blood cells that are too small. It is most often caused by iron deficiency, which can be addressed with diet or by treating underlying conditions that cause it. More rarely, it can be the result of genetic conditions.

Preventing anemia is important, especially if you are pregnant or menstruating, and involves ensuring sufficient dietary iron intake. You can get iron from red meat, poultry, fish, and various plant-based sources. Be particularly careful about iron intake if you choose not to eat meat.