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Thalassaemia trait
in the UK.

Thalassaemia trait is harmless for you, and important for your children if your partner carries it too. Here's who carries it in the UK, how NHS screening works, what your result means, and what to do before and during pregnancy.

By the DontMarryYourBro team · Updated November 2026 · 6 min read · How we fact-check

The short answer

  • Thalassaemia trait (also called thalassaemia minor) means you carry one changed gene. Carriers are healthy and need no treatment.
  • Common in families with roots in South Asia, Cyprus, Greece, Italy, the Middle East, China and Southeast Asia. An estimated 214,000 people in the UK carry it.
  • The NHS offers thalassaemia screening to every pregnant woman in England, ideally by 10 weeks.
  • If both partners carry beta thalassaemia, each pregnancy has a 1 in 4 chance of beta thalassaemia major.

What thalassaemia trait is

Thalassaemia is an inherited blood disorder that affects haemoglobin, the protein in red blood cells that carries oxygen. If you have thalassaemia trait, you carry one changed gene and one working one. You don't have the disease and it won't turn into it. Your red cells may be smaller than usual, which can look like mild anaemia on a blood test.

It matters for your children. If your partner also carries beta thalassaemia, each pregnancy has a 1 in 4 chance of a child with beta thalassaemia major, a serious condition usually treated with regular blood transfusions. More on what the trait means.

Who carries it in the UK?

Anyone can, but it's far more common in families from South Asia (Pakistan, India, Bangladesh), Cyprus, Greece, Italy, the Middle East, China and Southeast Asia. The UK National Screening Committee has estimated around 214,000 carriers in the UK. Many don't know.

How NHS screening works

  • In pregnancy: every pregnant woman in England is offered a blood test for thalassaemia, ideally by 10 weeks. Depending on where you live and your family origins, the same sample is also tested for sickle cell and other haemoglobin variants.
  • If you're a carrier: the baby's father is offered a test straight away.
  • If you're both carriers: you're offered counselling and a test of the pregnancy (CVS or amniocentesis), so you can make an informed decision.

The catch: by then you're already pregnant, and time is short. Testing before pregnancy gives you every option, including IVF with embryo testing.

Testing before pregnancy

  • Ask your GP for a full blood count and a haemoglobinopathy screen, especially if your family comes from a high-prevalence region or a relative has thalassaemia.
  • Test your partner too. One carrier alone doesn't put children at risk of thalassaemia major.
  • Watch the iron trap. Small red cells are also a sign of iron deficiency, so carriers are sometimes given iron they don't need, and iron deficiency can hide a carrier result. How to read the results.
  • Alpha thalassaemia often doesn't show on standard tests and may need a DNA test.

If you're both carriers

You can still have healthy children. A genetic counsellor can explain your options: testing in pregnancy, IVF with embryo testing (PGT-M, available on the NHS for some couples), donor eggs or sperm, or going ahead fully informed. Try the carrier odds calculator to see how the numbers work.

If you're related to your partner, a broader carrier screen is worth considering too. Cousin marriage in the UK.

General information, not medical advice. Speak to your GP, midwife or a genetic counsellor about your own results.

Sources

  1. GOV.UK: Sickle cell and thalassaemia screening handbook, antenatal screening
  2. GOV.UK: Sickle cell and thalassaemia screening pathway requirements
  3. Race Equality Foundation: Sickle cell and thalassaemia briefing (citing UK National Screening Committee estimates)
  4. Modell B, Darlison M. Global epidemiology of haemoglobin disorders. Bulletin of the WHO (2008)

Test as a couple, before pregnancy.

A couples carrier check covers thalassaemia and hundreds of other recessive conditions, with a genetic counsellor to explain the results.

Request a carrier check

Questions people ask.

What is thalassaemia trait?

Thalassaemia trait (or thalassaemia minor) means you carry one changed haemoglobin gene. Carriers are healthy and need no treatment, but if both partners carry beta thalassaemia, each pregnancy has a 1 in 4 chance of thalassaemia major.

Does the NHS test for thalassaemia?

Yes. Every pregnant woman in England is offered a thalassaemia screening blood test, ideally by 10 weeks. If she is a carrier, the baby's father is offered a test.

Can I get tested for thalassaemia before pregnancy?

Yes. Ask your GP for a full blood count and haemoglobinopathy screen, especially if your family comes from a region where thalassaemia is common or a relative has it.

Is thalassaemia trait a disease?

No. Thalassaemia trait is a carrier state. It can cause slightly small red cells but usually no symptoms, and it never turns into thalassaemia major.

Should my partner be tested?

Yes. The risk to children depends on both partners. If you carry thalassaemia trait, your partner's result decides whether your children could be affected.