Tests and diagnosisBy Mayo Clinic staff
Newborn blood testing identifies almost all cases of PKU. All 50 states in the United States require newborns to be screened for PKU. Many other countries also routinely screen infants for PKU.
If you have PKU or a family history of PKU, your doctor may recommend screening tests before pregnancy or birth. It's possible to identify PKU carriers through a blood test.
Testing your baby after birth
A PKU test is conducted a day or two after your baby's birth. In the test, a nurse or lab technician collects a few drops of blood from your baby's heel or the bend in your baby's arm using a needle or lancet. A laboratory tests the blood sample for certain metabolic disorders, including PKU. The test isn't done before the baby is 24 hours old or before the baby has ingested some protein in the diet to ensure accurate results. If you don't deliver your baby in a hospital or are discharged soon after the birth, you may need to schedule a newborn screening with your pediatrician or family doctor.
Your baby may also have additional tests to confirm the diagnosis, including more blood tests and urine tests. You and your baby may also undergo genetic testing to identify gene mutations.
If your baby's blood sample shows a high level of phenylalanine, he or she will need to be fed a special formula. Your doctor and dietitian can help you find the right type of formula to feed your baby.
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