The Newborn Bloodspot Test (Heel Prick): What It Screens For and What Happens Next

Within the first week of your baby's life, a midwife will offer to perform the newborn bloodspot screening test — sometimes called the heel prick test. It is one of the most important public health screening tests in the UK and has been transforming outcomes for children with rare but serious conditions since 1969.

Understanding what the test is for, how it works, and what the process looks like if a result needs follow-up will help you feel informed and prepared.

When Is the Test Done

The test is offered to all newborns in the UK. It is performed on day 5 of life (with day one being the day of birth). It is done on day 5 rather than earlier because some of the conditions screened — particularly phenylketonuria (PKU) — only produce detectable markers after the baby has been feeding for several days.

If your baby was born prematurely or spent time in neonatal intensive care, the test may be done at a different time or repeated. Premature babies may need multiple bloodspot tests as their results can be more difficult to interpret.

The test is performed by a midwife, either in hospital before discharge or during a home visit. A small lancet is used to prick the heel — the outer edge of the heel, not the centre — and a few drops of blood are collected onto a special absorbent card (a Guthrie card). Four spots are collected. The card is labelled and sent to a laboratory.

What the Test Screens For

The NHS Newborn Bloodspot Screening Programme currently screens for nine conditions. All of them are serious but treatable — and that is the whole point. Early identification before symptoms develop allows treatment to begin promptly, preventing significant harm.

1. Congenital Hypothyroidism (CHT)

The thyroid gland is underactive or absent. Without treatment, hypothyroidism causes profound intellectual disability, growth failure, and deafness. With early thyroxine replacement, children develop normally. This is the most common condition detected — approximately 1 in 2,000 babies.

2. Phenylketonuria (PKU)

The body cannot process phenylalanine, an amino acid found in protein. Without a strict low-phenylalanine diet started early, it accumulates and causes severe brain damage. With dietary management — and newer drug treatments (sapropterin, pegvaliase) — most people with PKU live entirely normal lives. Affects approximately 1 in 10,000 babies.

3. Sickle Cell Disease (SCD)

A group of inherited conditions affecting haemoglobin, causing episodes of severe pain, anaemia, infection risk, and organ damage. Early identification allows prophylactic penicillin (to prevent severe infections), parental education, and specialist follow-up that dramatically improves outcomes. Affects approximately 1 in 2,000 babies, with much higher rates in babies of African and Caribbean ancestry.

4. Cystic Fibrosis (CF)

A genetic condition affecting the lungs, digestive system, and other organs. Early diagnosis allows treatment to start before symptoms cause significant lung damage, dramatically improving quality of life and life expectancy. Affects approximately 1 in 2,500 babies.

5. Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD)

The body cannot break down fats for energy when glucose is unavailable — for example, during an illness or fasting. This can cause metabolic crises, seizures, brain damage, or sudden death. With dietary management (avoiding fasting) and emergency protocols, it is entirely manageable. Affects approximately 1 in 10,000–20,000 babies.

6. Maple Syrup Urine Disease (MSUD)

The body cannot process certain amino acids (leucine, isoleucine, valine). Without a specialised low-protein diet, it causes brain damage and, in acute crises, can be life-threatening. Affects approximately 1 in 100,000–200,000 babies.

7. Isovaleric Acidaemia (IVA)

An organic acid disorder — the body cannot break down the amino acid leucine properly. Can cause vomiting, lethargy, and metabolic crises. Managed with dietary restrictions and supplements.

8. Glutaric Aciduria Type 1 (GA1)

A metabolic condition that can cause sudden neurological damage during childhood illnesses (encephalopathic crises). Early identification allows parents to follow an emergency protocol during illness, protecting the child from brain injury. Most adults with GA1 who were identified early and managed appropriately have no significant neurological disability.

9. Homocystinuria (HCU) — Pyridoxine non-responsive

A metabolic disorder causing elevated homocysteine, which damages blood vessels and the lens of the eye, and can cause learning difficulties. Managed with a low-methionine diet and supplements.

How Results Are Communicated

Most parents will receive no communication at all — which is the good news. If screening does not identify any concerns, you will be notified by letter or via your GP/health visitor, usually within six to eight weeks of the test. In some areas, no news is good news and you may not receive an explicit letter unless your GP's practice is particularly proactive.

If a result requires follow-up, you will be contacted promptly — usually by phone — by your GP, health visitor, or a specialist team. You should not have to wait weeks in uncertainty.

What a Positive (Abnormal) Result Means

An abnormal bloodspot result does not necessarily mean your baby has the condition. Screening tests are designed to be sensitive — they catch as many true cases as possible — which means some positive results are false positives. A positive result triggers further diagnostic testing to confirm or rule out the diagnosis.

Your baby will be referred urgently to a specialist team. They will repeat blood tests and may carry out other investigations. In some conditions (particularly CHT and MCADD), treatment may be started while confirmatory tests are awaited rather than waiting for a definitive diagnosis, because the risk of harm from delay is high.

Receiving a call about an abnormal result is frightening. It helps to know:

• Most follow-up results turn out to be false positives
• Even if the condition is confirmed, most conditions found on newborn screening are highly manageable with early treatment
• You will be supported by a specialist team with expertise in the condition

Declining the Test

You can decline the newborn bloodspot test. It is not mandatory. However, the NHS and all professional bodies strongly recommend it, because the benefit of early detection far outweighs the minimal discomfort of the heel prick. If you have any concerns about any aspect of the screening, discuss them with your midwife or health visitor before making a decision.