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Understanding Phenylketonuria (PKU)
PKU, or phenylketonuria, is a genetic metabolic condition that affects how the body processes protein. It is caused by changes in the PAH gene, which normally helps produce an enzyme called phenylalanine hydroxylase.
When this enzyme does not work properly, the amino acid phenylalanine (Phe) cannot be processed efficiently and builds up in the blood. Over time, high levels of phenylalanine can affect the brain and nervous system.
Important: PKU exists on a spectrum, and each person may have different treatment needs, Phe tolerance levels, monitoring schedules, and therapy options. Your metabolic clinic will guide the plan that is appropriate for you or your child.
Jump to:
Detection |
Without treatment |
How it is managed |
Treatments and therapies |
Tools |
Helpful links |
Next steps
How is PKU detected?
PKU is identified through newborn screening across Canada. Babies with PKU often appear healthy at birth. A simple blood test in the first days of life can detect elevated phenylalanine levels.
Early identification allows families and clinics to begin management right away, supporting healthy growth and brain development.
What happens without treatment?
Without management, phenylalanine can build up quickly. Historically, untreated PKU caused significant neurological and developmental complications. Today, early diagnosis and ongoing care help people with PKU thrive.
How is PKU managed?
PKU management focuses on keeping blood phenylalanine levels in a safe range. This often includes:
- A phenylalanine-restricted diet
- Medical nutrition, including formula, to meet protein and nutrient needs
- Regular blood monitoring
- Ongoing guidance from your metabolic clinic
Important: Tracking methods can differ by clinic, including exchanges, grams, total protein, or formula-based systems. Always follow your clinic's guidance and ask questions if you are unsure.
Key idea:
PKU management has changed significantly over time. Many individuals and families today use a combination of nutrition strategies, monitoring, medical foods, supplements, and therapies to support long-term health and quality of life.
PKU management has changed significantly over time. Many individuals and families today use a combination of nutrition strategies, monitoring, medical foods, supplements, and therapies to support long-term health and quality of life.
Treatments and therapies
PKU care has evolved over time. If you want more detail on treatments, approvals, medication access, and emerging therapy options, visit:
Tools
Tip: Click a dropdown to discover resources. We will continue expanding these over time.
Monitoring your Phe levels
Many clinics use home blood spot cards to track phenylalanine levels. Your clinic will tell you how often to test, where to send samples, and what targets apply to your age and treatment plan.
NSPKU Blood Sampling Video
Rosie's Blood Spot Video
Brian's Blood Spot Video
Helpful links - global and regional PKU support
Canada
United States - National
United States - Regional and Partner Organizations
- New England Connection for PKU and Allied Disorders (NECPAD)
- Intermountain PKU and Allied Disorders (IPAD)
- Mid-Atlantic Connection for PKU and Allied Disorders (MACPAD)
- Minnesota PKU
United Kingdom
Europe
External links are shared for community connection and education. Always confirm medical guidance with your metabolic clinic.
Where would you like to go next?
Last updated: May 2026. Information on this page is intended for general education and community support. Medical care, nutrition plans, medications, and treatment decisions should always be confirmed with your metabolic clinic. To suggest updates, contact website@canpku.org.