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Understanding Phenylketonuria (PKU)

PKU (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.

Jump to: Detection | Without treatment | How it is managed | Tools | 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 (formula) to meet protein and nutrient needs
Regular blood monitoring
Ongoing guidance from your metabolic clinic

Important: Tracking methods can differ by clinic (exchanges vs grams vs total protein vs formula rules). Always follow your clinic’s plan and ask if you are unsure.

Treatments and Therapies

PKU care has evolved over time. If you want more detail on treatments, approvals, and emerging options, visit:

PKU Treatments and Therapies

Tools

Tip: Click a dropdown to discover resources. We will expand 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