Phenylketonuria (PKU) Screening Test
A PKU screening test measures the amount of phenylalanine (Phe) in a newborn's blood to check for phenylketonuria (PKU), a rare genetic disorder. High levels of Phe may indicate PKU, which can cause brain damage if not treated early.
What this test measures
The PKU screening test measures the amount of a protein called phenylalanine (Phe) in a sample of a newborn's blood.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
If your baby's results are not normal, it means high levels of Phe were found in your baby's blood. Your baby most likely has PKU. Your provider may order more tests to confirm or rule out PKU.
Frequently asked questions
What is PKU?
PKU is a rare genetic disorder that makes it hard for the body to break down a protein called phenylalanine (Phe). High levels of Phe can damage the brain.
Why is PKU screening done on all newborns?
The test is easy and has almost no health risks, and doing the test may save a baby from lifelong brain damage or other serious health problems.
What does a normal PKU test result mean?
A normal result means the amount of Phe in your baby's blood was normal, so your baby is unlikely to have PKU. But if the test was done sooner than 24 hours after birth, your baby may need to be tested again at 1 to 2 weeks of age.
What does an abnormal PKU test result mean?
An abnormal result means high levels of Phe were found in your baby's blood. Your baby most likely has PKU, and your provider may order more tests to confirm.
How is PKU treated?
If your baby is diagnosed with PKU, you can safely give your baby formula that doesn't contain Phe. After infancy, people with PKU are generally treated with a special low-protein diet and food supplements.
Related lab tests
Sources
- MedlinePlus: Phenylketonuria (PKU) Screening — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.