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Sickle cell trait
in the UK.

Sickle cell trait means you're a healthy carrier. It matters most when your partner is a carrier too. Here's who carries it in the UK, how NHS pregnancy and newborn screening works, and what to do with your result.

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

The short answer

  • Sickle cell trait (HbAS) means you carry one sickle gene. Carriers are healthy and don't develop sickle cell disease.
  • Common in families with roots in Africa, the Caribbean, the Middle East, parts of India and the Mediterranean. An estimated 240,000 people in the UK carry it.
  • The NHS screens in pregnancy and at birth: every newborn's heel-prick test checks for sickle cell disease.
  • If both partners carry it, each pregnancy has a 1 in 4 chance of sickle cell disease.

What sickle cell trait is

Sickle cell disease is an inherited condition in which red blood cells become stiff and sickle-shaped, causing pain, anaemia and infections. If you have sickle cell trait, you carry one sickle gene and one usual gene. You don't have the disease and won't develop it. Very rarely, carriers can have problems under extreme conditions such as severe dehydration or very high altitude. More on sickle cell trait.

Who carries it in the UK?

It's most common in people with family roots in sub-Saharan Africa and the Caribbean, and also found in families from the Middle East, parts of India and the Mediterranean. The UK National Screening Committee has estimated around 240,000 carriers in the UK. Sickle cell disease is one of the most common inherited conditions in the country.

How NHS screening works

  • In pregnancy: in areas where sickle cell is more common, every pregnant woman is offered a blood test. Elsewhere, a family origin questionnaire about both parents decides who is offered testing. The aim is to test by 10 weeks.
  • If the mother is a carrier: the baby's father is offered a test.
  • If both are carriers: counselling and a test of the pregnancy are offered.
  • At birth: the newborn heel-prick (blood spot) test checks every baby for sickle cell disease. It can also show if your baby is a carrier, which tells you that at least one parent is.

Testing before pregnancy

You can ask your GP for a haemoglobinopathy blood test at any time. If you know you're a carrier, ask your partner to get tested before you try for a baby: it gives you the most time and the most options. Carrier screening that covers sickle cell alongside thalassaemia and other conditions is also available privately.

What two results mean together

Partner 1Partner 2Each pregnancy
Sickle cell traitNot a carrierNo sickle cell disease. 1 in 2 chance the child is a carrier
Sickle cell traitSickle cell trait1 in 4 chance of sickle cell disease
Sickle cell traitBeta thalassaemia trait1 in 4 chance of sickle beta thalassaemia
Sickle cell traitHbC trait1 in 4 chance of HbSC disease

If you're both carriers, a genetic counsellor can talk you through testing in pregnancy, IVF with embryo testing, donor options, or going ahead informed. Thalassaemia trait 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)

Know before you plan.

A couples carrier check covers sickle cell, thalassaemia and hundreds of other conditions, with a genetic counsellor included.

Request a carrier check

Questions people ask.

What is sickle cell trait?

Sickle cell trait means you carry one sickle gene. Carriers are healthy and do not develop sickle cell disease, but if both partners are carriers, each pregnancy has a 1 in 4 chance of sickle cell disease.

Does the NHS test for sickle cell?

Yes. Pregnant women are offered screening (all women in higher-prevalence areas, and based on a family origin questionnaire elsewhere), and every newborn is checked through the heel-prick blood spot test.

Can I get a sickle cell test from my GP?

Yes. You can ask your GP for a haemoglobinopathy blood test at any time, ideally before pregnancy.

How many people in the UK have sickle cell trait?

The UK National Screening Committee has estimated around 240,000 carriers in the UK. It is most common in people with African and Caribbean family roots.

Can two people with sickle cell trait have children?

Yes. Each pregnancy has a 3 in 4 chance of a child without sickle cell disease. Couples can talk to a genetic counsellor about testing in pregnancy or IVF with embryo testing.