Thalassemia: Understanding Your Pathology Report

Section Editor: Kamran Mirza MD PhD
July 6, 2026

Thalassemia is a group of inherited blood disorders in which the body makes less of one of the protein chains that build hemoglobin, the substance inside red blood cells that carries oxygen. Normal adult hemoglobin is made of two alpha-globin chains and two beta-globin chains. When the body cannot make enough of one of these chains, the red blood cells become small and pale and do not survive as long as they should, leading to a shortage of healthy red blood cells (anemia). Thalassemia ranges from a silent carrier state that causes no symptoms to a severe form that requires lifelong treatment, and it is usually identified through blood tests that examine the red blood cells and the different types of hemoglobin.

This article will help you understand the blood test and hemoglobin analysis results used to diagnose thalassemia, what each term means, and why it matters for your care.

What causes thalassemia?

Thalassemia is caused by inherited changes in the genes that provide instructions for making the globin chains of hemoglobin. It is passed down from parents to children, and the severity depends on how many genes are affected. There are two main types, based on which chain is reduced:

Beta-thalassemia — Changes in the HBB gene that decrease or halt beta-globin chain production cause this condition. Since an individual has two beta-globin genes, the extent of the effect depends on how many are affected, which influences the severity.
Alpha-thalassemia — This condition results from the loss of one or more of the four alpha-globin genes, leading to decreased production of alpha-globin chains. The severity increases with the number of missing genes.

What are the types of thalassemia?

Doctors describe thalassemia by which chain is affected and how severe it is. The beta-thalassemia types include:

Beta-thalassemia minor (trait) — One beta-globin gene is affected. This usually causes mild anemia or no symptoms, and the person is a carrier.
Beta-thalassemia intermedia — A moderate form that may need occasional treatment but does not always require regular transfusions.
Beta-thalassemia major (Cooley anemia) — Both beta-globin genes are severely affected, causing severe anemia that begins in early childhood and requires lifelong treatment.

The alpha-thalassemia types depend on how many of the four alpha-globin genes are missing:

Silent carrier — One gene missing. There are usually no symptoms and normal blood counts.
Alpha-thalassemia trait — Two genes missing. This causes mild anemia with small red blood cells, similar to beta-thalassemia trait.
Hemoglobin H disease — Three genes missing. This leads to moderate-to-severe anemia due to the breakdown of red blood cells.
Hemoglobin Bart (hydrops fetalis) — All four genes missing. This is the most severe form and is usually fatal before or shortly after birth.

What are the symptoms of thalassemia?

The symptoms of thalassemia depend on the type and severity. People with a trait or carrier state usually have no symptoms or only mild anemia, which is discovered on a routine blood test. People with more severe forms, such as beta-thalassemia major, develop significant anemia early in life, with fatigue, paleness, poor growth, and an enlarged spleen and liver. Over time, the bone marrow works harder to make red blood cells, which can cause changes in the bones. People who need frequent blood transfusions can also develop iron overload, a buildup of excess iron that can damage the heart, liver, and other organs.

How is the diagnosis made?

Thalassemia is diagnosed with blood tests, and in many places it is first suspected when a routine complete blood count (CBC) shows small red blood cells. The red blood cells in thalassemia are typically microcytic (smaller than normal) and hypochromic (paler than normal), as indicated by a low mean corpuscular volume (MCV). A blood smear, a thin layer of blood examined under the microscope, often shows these small, pale cells along with target cells (red blood cells with a bullseye appearance) and other changes, which a pathologist can recognize.

The key test is hemoglobin analysis, which separates and quantifies the different hemoglobin types using methods such as hemoglobin electrophoresis, high-performance liquid chromatography (HPLC), and capillary electrophoresis. Iron studies are also important because they are usually normal in thalassemia, helping distinguish it from iron deficiency (another common cause of small red blood cells). Because alpha-thalassemia often does not change the hemoglobin analysis pattern, genetic (DNA) testing is frequently needed to confirm it, and DNA testing is also used to confirm the exact type of beta-thalassemia and for family planning and carrier testing.

What do the hemoglobin analysis and blood tests show?

The hemoglobin analysis report lists the different hemoglobins in the blood and their percentages. The pattern depends on the type of thalassemia:

Beta-thalassemia trait — A raised level of hemoglobin A2 (usually above 3.5%) is the classic finding, sometimes accompanied by a mildly elevated hemoglobin F (fetal hemoglobin).
Beta-thalassemia major — Little or no normal adult hemoglobin (hemoglobin A), with a large amount of hemoglobin F.
Alpha-thalassemia — The hemoglobin analysis is often normal, so the diagnosis usually depends on genetic testing. In the more severe forms, abnormal hemoglobins called hemoglobin H or hemoglobin Bart may be detected.

The blood count and iron studies add important information. In thalassemia, the red blood cells are small (low MCV), the red blood cell count is often normal or even high, and iron studies are usually normal. This combination helps distinguish thalassemia from iron deficiency, as described in the next section.

How is thalassemia different from iron deficiency anemia?

Both thalassemia and iron deficiency anemia cause small, pale red blood cells, so they can look similar on a complete blood count. The key difference is in the iron studies. In iron deficiency, the body’s iron stores are low, so tests such as ferritin and serum iron are reduced. In thalassemia, iron levels are usually normal, and in beta-thalassemia trait, hemoglobin A2 levels are often elevated. Making this distinction matters, because taking iron supplements does not help thalassemia and can be harmful if too much iron builds up. An iron panel is often used to distinguish between these two conditions.

What happens after a diagnosis of thalassemia?

After thalassemia is diagnosed, treatment depends on the type and severity. The blood and hemoglobin findings help guide several decisions:

Trait or carrier state — Usually no treatment is needed. Genetic counseling is helpful for family planning, and unnecessary iron supplements should be avoided unless iron deficiency is also present.
Moderate forms — May be managed with folic acid, monitoring, and occasional blood transfusions during times of increased need.
Severe forms (such as beta-thalassemia major) — Regular blood transfusions are combined with iron chelation therapy, which removes excess iron that accumulates from repeated transfusions. A medicine called luspatercept can reduce the need for transfusions in some people.
Potentially curative treatments — An allogeneic stem cell transplant, using blood-forming cells from a donor, can cure severe thalassemia. Newer gene therapies, which modify a person’s own blood-forming cells, have also become available for transfusion-dependent beta-thalassemia.

Care is usually provided by a team experienced in blood disorders, and regular monitoring helps manage anemia and prevent complications of iron overload. Clinical trials of newer treatments may also be an option to discuss. Decisions about treatment are made by the care team together with the patient, based on the type of thalassemia and the specific findings.

What is the prognosis for thalassemia?

The outlook for thalassemia depends on the type. People with a trait or carrier state have a normal life expectancy and generally no health problems from the condition. People with severe forms, such as beta-thalassemia major, once had a limited outlook, but modern treatment with regular transfusions and iron chelation has greatly improved both survival and quality of life. Stem cell transplant and gene therapy now offer the possibility of a cure for some people. Your outlook depends on the type of thalassemia and your treatment, which your health care team can explain in the context of your specific situation.

Questions to ask your doctor

What type of thalassemia do I have?
Do I have a thalassemia trait (carrier) or a form that needs treatment?
What did my hemoglobin analysis show, including my hemoglobin A2 level?
Were my iron studies checked, and were they normal?
Could my small red blood cells be due to iron deficiency rather than, or in addition to, thalassemia?
Was genetic testing done to confirm my diagnosis?
Will I need blood transfusions, and if so, how often?
How will iron overload be monitored and managed?
Am I a candidate for a stem cell transplant or gene therapy?
Should my family members be tested for thalassemia?
Are there clinical trials that I should consider?