Phenylketonuria (PKU) Test

Phenylketonuria (PKU) Test

What To Think About

  • When the PKU test is done within 24 hours of birth, there is a small chance that the test result will not be accurate (false-negative or false-positive). Your baby may need to be tested again. There is less chance of a false result if the test is done between 24 and 72 hours after birth.
  • If your baby has PKU, he or she will need regular blood tests to check phenylalanine levels. These tests may occur as often as once a week in your baby's first year and then once or twice a month throughout childhood.
  • A blood test for phenylalanine may be done if you have PKU and plan to become pregnant. If you eat too much protein, you will have high levels of phenylalanine in your blood. If you become pregnant, the high levels of phenylalanine could cause your baby (fetus) to have intellectual disability, even if your baby does not have PKU. It is important that everyone with PKU see a specialist for nutritional counseling. Phenylalanine levels should be below 6 mg/dL at least 3 months before you become pregnant. Recommended phenylalanine levels during pregnancy are 2 mg/dL to 6 mg/dL, and you should be tested at least once a week.
  • A test for phenylalanine levels in urine may be done if your baby is now over 6 weeks of age and did not have a PKU blood test 2 to 3 days after birth. A PKU heel stick can be done up to 6 weeks of age and has better results than a urine test. A urine test may be done to check phenylalanine levels during treatment with low-protein foods.
  • If your baby has PKU, a special low-protein diet is needed to prevent intellectual disability. Your baby will drink milk substitutes that do not contain phenylalanine. People with PKU need to stay on a low-protein diet for life to prevent problems.
Author:
Healthwise Staff
Medical Review:
John Pope, MD - Pediatrics
Chuck Norlin, MD - Pediatrics
Last Updated:
June 19, 2012
Healthwise
Help
Healthwise Index
Topic Contents
Test Overview
Why It Is Done
How To Prepare
How It Is Done
How It Feels
Risks
Results
What Affects the Test
What To Think About
Related Information
References
Credits
View Entire Topic
©1995-2012, Healthwise, Incorporated, P.O. Box 1989, Boise, ID 83701.
ALL RIGHTS RESERVED

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information. For more information, click here.
How this information was developed.