Thalassaemia trait or iron deficiency? Why testing comes before treatment

A common confusion

On a complete blood count, both iron deficiency and thalassaemia trait can show small red cells (low MCV and MCH) and sometimes a mildly low haemoglobin. Because the CBC looks similar, people are often given iron tablets without further testing. That can be unhelpful, because thalassaemia trait does not improve with iron.

What is thalassaemia trait?

Thalassaemia is an inherited condition that affects how haemoglobin is made. A carrier, who has "trait", has inherited one changed gene. It is relatively common in South Asia and many other parts of the world. Most people with trait feel well, but trait can matter when two carriers have children, so doctors often discuss family screening.

How doctors tell them apart

1. Iron tests such as ferritin show whether iron stores are truly low.
2. The CBC pattern, including the red cell count and distribution width, gives clues.
3. Haemoglobin analysis (such as HPLC or electrophoresis) can identify thalassaemia trait and some other haemoglobin variants.
4. Family history and sometimes genetic testing help when the picture is not clear.

What this means for you

• Ask for iron tests before starting iron, if you have small red cells on your CBC.
• If iron is low, treat it and find the cause.
• If iron is normal and the red cells stay small, ask about haemoglobin analysis.
• If trait is confirmed, ask whether partners or family members should be screened.

When to seek urgent care

Fainting, severe breathlessness, chest pain or a new yellow tinge to the eyes with severe weakness need prompt medical care.

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Frequently asked questions