Newborn blood spot screening FAQs

All your questions about newborn blood spot screening answered, including what happens to your baby's blood spot card and why a second sample is sometimes needed.

Why does blood have to be taken when babies are only about a week old?

Every baby is offered newborn blood spot screening, also known as the heel prick test, ideally when they are 5 days old. Newborn babies are screened for: 

This is the best time to test for all the conditions together. It allows time to get the results back, do diagnostic tests if required and start any necessary treatment early.

If babies were tested later, some babies might suffer harm that could have been avoided if they had been tested earlier.

Babies who are new to the country or are yet to have a heel prick test are able to have the test at any time up to 1 year old. However, this does not include the cystic fibrosis screening test, which is not reliable after 8 weeks of age.

Newborn siblings of children affected by 1 of the conditions can be tested for that specific condition earlier than 5 days old. Another sample can then be taken on day 5 to screen for the other conditions.

Read more about newborn blood spot tests and what the blood spot test involves.

When should premature babies be screened?

Babies admitted to hospital before day 5, perhaps because they are premature or unwell, should have a blood spot sample taken on admission. This sample will be used to screen for sickle cell disease in case the baby has a blood transfusion.

Babies who are premature or unwell, or have had blood transfusions, should have the usual blood spot sample taken on day 5. This blood sample is recorded on the blood spot card, along with other information.

If a baby is born before 32 weeks, an additional test is needed for congenital hypothyroidism at 28 days of age or when they are discharged from hospital, whichever is sooner. The British Thyroid Foundation has more information about congenital hypothyroidism.

newborn blood spot screening
Newborn blood spot screening

When is a second sample needed?

Occasionally, your midwife or health visitor will contact you and ask to take a second blood sample from your baby's heel. This may be because not enough blood was collected, or the result was borderline or unclear.

It may also be because your baby was premature. In babies born before 32 weeks of pregnancy, testing on day 5 may not pick up congenital hypothyroidism. It's advisable to have another test – either at 28 days of age or before your baby is discharged home, whichever is sooner. The repeat results are usually normal.

Are any of the conditions tested for during pregnancy?

During pregnancy, you will be screened for sickle cell disease. It's possible to screen for carriers of cystic fibrosis in pregnancy, but this is not currently done in the UK.

I have been told my baby is a carrier. What does this mean for my baby and my family?

Carrier status is very common and does not mean your baby will become ill.

For your baby:

For your family:

If we move to a new area, will health professionals need proof that my baby has had the screening test?

If you move to a new area while your baby is less than 1 year old, you will need to provide confirmation to a GP or health visitor that they have been screened. This could be a written copy of their results, or results written in the personal child health record.

If you have moved from abroad and no proof of testing is available, retesting can be discussed with you and arranged with your consent.

What are newborn blood spot cards?

As well as being used to take blood samples, these cards record personal information, including a baby's name, date of birth, address and NHS number; the mother's name; and contact details of the GP and midwife. These are needed to make sure the results of the screening tests are matched to the right baby.

What happens to my baby's blood spot card?

After screening, the blood spot cards are stored for at least 5 years. They may be used:

This research will not identify your baby, and the use of these blood spots is covered by a code of practice, which is available from your midwife or can be seen on the GOV.UK website.

There is a small chance researchers may want to invite you or your child to take part in research linked to this screening programme. If you do not want to be invited, please let your midwife know.

If it looks like you or your baby has sickle cell disease or thalassaemia, information will be passed to the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS). This helps to improve screening and prevention or treatment of the condition.

You can opt out of the register, or find out more, by visiting and

You can find out more about why blood spot cards are stored and how your baby's personal information is protected in Newborn blood spot cards explained.

Page last reviewed: 10 August 2020
Next review due: 10 August 2023