People with thalassemia trait usually don’t have any symptoms. In certain cases, like during pregnancy, thalassemia carriers may have symptoms of mild anemia, such as fatigue or headaches.

Thalassemia is a genetic disease that reduces your body’s ability to produce healthy hemoglobin.

Alpha- and beta-thalassemia disease can cause serious illness and require ongoing care, but having thalassemia trait, also known as being a “thalassemia carrier,” is different.

Experts estimate that about 5% of the world’s population carries the alpha-thalassemia trait, and 1.5% carries the beta-thalassemia trait.

Research indicates that being a thalassemia carrier occurs more frequently in people who have African, Indian, Mediterranean, Middle Eastern, and Southeast Asian backgrounds. Scientists believe the trait helps protect against malaria infection.

People with thalassemia trait typically won’t have any symptoms and can’t go on to develop thalassemia disease themselves. But, because they can pass thalassemia gene mutations on to their children, they’re called “carriers.”

You inherit the genes responsible for building healthy hemoglobin from your parents. The specific types of thalassemia, depending on carriers, are:

  • Alpha-globin gene: 4 copies (2 from each parent) located on chromosome 16
  • Beta-globin gene: 2 copies (1 from each parent) located on chromosome 11

To develop alpha-thalassemia disease, you’d need to inherit three or more faulty alpha-globin genes. To develop beta-thalassemia disease, both of your beta-globin genes must be mutated.

But, many people who inherit a smaller number of thalassemia gene mutations won’t have thalassemia disease. Instead, they’re thalassemia mutation carriers. Depending on which genes are affected, a doctor may diagnose alpha- or beta-thalassemia trait.

If you’re a thalassemia carrier, you’ll still make enough functional hemoglobin to stay healthy, but you can pass the thalassemia genes on to your children.

Alpha-thalassemia trait

Alpha-thalassemia trait can occur when you inherit one or two affected alpha-globin genes. Alpha-thalassemia trait can mean either:

  • Alpha-thalassemia minima/silent carrier: Only one of your four alpha-globin genes is affected. You generally won’t have any symptoms and may not have any noticeable laboratory findings.
  • Alpha-thalassemia minor: With two missing or mutated alpha-globin genes, your body can make about half the typical amount of alpha-globin, but your bone marrow can compensate and make enough hemoglobin to keep you healthy.

Beta-thalassemia trait

In this condition, which can also be called “beta-thalassemia minor,” one of your two beta-globin genes is mutated. Researchers have identified more than 200 such mutations with a range of severities.

Because your second beta-globin gene is still fully functional, you usually won’t experience any symptoms.

Usually, none. In both alpha- and beta-thalassemia traits, you could have persistent mild anemia, but this usually won’t cause any symptoms. A doctor may notice specific findings on blood tests, such as smaller red blood cells (RBCs) or a change in their appearance.

When symptoms do occur, they’re usually similar to symptoms of mild anemia, including:

  • fatigue
  • pale skin
  • headaches
  • dizziness
  • weakness

Symptoms and signs might be more noticeable in special cases. For example, according to one 2022 study, it was noted that thalassemia trait can increase your risk of anemia or high blood pressure in pregnancy.

A doctor can help regularly check you for any unusual complications.

People with thalassemia trait typically don’t require treatment.

Although you may have mild anemia, people with thalassemia trait don’t benefit from iron supplements unless they also have iron deficiency. A doctor can check an iron storage level (ferritin test) to confirm.

Sometimes, people co-inherit the thalassemia trait with other hemoglobin mutations, such as sickle cell trait. In these cases, symptoms may be present, and you may need treatment.

If thalassemia runs in your family or you have a thalassemia trait that has been diagnosed, a doctor can refer you for genetic counseling to learn more about any risks to your future children.

If you have a family history of thalassemia or have a thalassemia trait that has been diagnosed, be sure to let a doctor know.

Thalassemia trait can look like iron deficiency anemia on a complete blood count (CBC), but most people with thalassemia trait don’t have iron deficiency and don’t require iron supplements.

If you have thalassemia trait and mild anemia, a doctor will need to check iron tests before deciding whether you need iron supplements.

The most important precaution for people with thalassemia trait concerns family planning.

Genetic counseling is important because you can pass on thalassemia genes even if you have no symptoms. If both you and your partner have thalassemia trait or other hemoglobin mutations, there’s a chance your child could be born with more severe thalassemia disease.

How do you test for thalassemia carrier status?

Doctors can test for thalassemia trait (also called “carrier status”) with blood tests, including:

  • Complete blood count: CBC results may be typical or might show mild anemia (low hemoglobin) with small RBCs. A Mentzer index (mean corpuscular volume divided by RBC count) lower than 13 is consistent with thalassemia trait.
  • Peripheral blood smear: A blood smear may show small, pale RBCs along with other RBC findings such as poikilocytosis.
  • Iron studies: It can be hard to tell thalassemia trait apart from mild iron deficiency anemia. In thalassemia, iron storage levels are usually typical or mildly high.
  • Hemoglobin analysis: Doctors can use electrophoresis or high-performance liquid chromatography to analyze the hemoglobin types and amounts in your blood and to diagnose thalassemia trait.
  • Genetic tests: Genetic testing can find specific alpha- or beta-thalassemia gene mutations, making a definitive diagnosis.
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Thalassemia carriers (people who carry the trait for either alpha- or beta-thalassemia) don’t develop the disease but can pass on the gene mutations to their children.

If you’re a thalassemia carrier, a doctor may notice that you have persistently mild anemia with smaller RBCs, but these are unlikely to cause symptoms or require treatment.

While thalassemia trait generally won’t affect your overall health, it can occasionally cause issues in pregnancy, such as high blood pressure or worsened anemia. A doctor can help screen for these conditions.

It’s important to let a doctor know you have thalassemia trait. If thalassemia runs in your family, you can ask to undergo testing. Knowing your carrier status may help a doctor avoid unnecessary treatments and will help them guide you with any desired family planning.