What Is PKU?
If you’re new to my blog, you’re probably wondering: What the heck is PKU?

Here’s what I tell people when they ask:

PKU, or Phenylketonuria, is a rare inherited metabolic disorder. It’s usually diagnosed shortly after birth through newborn screening — often called the heel-prick test. People with PKU are born without the enzyme needed to break down phenylalanine (Phe), an essential amino acid found in protein.

In a typical body, Phe is converted into tyrosine, which is then used to produce neurotransmitters in the brain. But with PKU, this conversion doesn’t happen. As a result, Phe builds up in the bloodstream and brain, becoming toxic. High Phe levels can cause a wide range of symptoms, including:

Cognitive impairments

Anxiety and depression

Poor focus and memory

Developmental delays

Fine motor skill issues

And more

The Lifelong PKU Diet
To prevent these harmful effects, people with PKU must follow a low-protein diet for life, along with drinking a medical formula that provides the nutrients we can’t get from high-protein foods. This formula is specially designed to be Phe-free and provides the amino acids our bodies need, minus the one we can’t process.

Low-protein medical foods — such as special breads, pastas, and baking mixes — are also essential. Without them, the PKU diet would be mostly limited to fruits and vegetables, making it extremely difficult to meet energy and nutrient needs.

These medical foods and formulas are not optional — they are prescription treatments. In British Columbia, we are fortunate to receive a monthly low-protein food subsidy (thanks in part to advocacy efforts and support from former Health Minister Terry Lake), and formulas are covered under provincial health plans. However, access and funding vary across Canada and need improvement.

Managing PKU Day-to-Day
Every bite of food I eat is weighed, measured, and tracked. I used to write everything down in a notebook — now I use howmuchphe.org, a fantastic resource for tracking Phe intake and food values.

Just like people with diabetes, I regularly monitor my levels — but unlike diabetics, I don’t have access to a home test device. I have to do a finger prick, fill out a blood dot card (the same kind used for newborn screening), and mail it to BC Children’s Hospital. It takes 10–14 days to get results. If my levels are high, the damage is already done by the time I find out.

It’s my dream that one day, we’ll have real-time home testing — a game-changer not just for everyday management but especially for maternal PKU, where strict control is crucial for a healthy pregnancy. (More on that in another post.)

A Genetic Condition with a 25% Chance
PKU is genetic and autosomal recessive, which means both of my parents were carriers. I have four siblings, and none of them have PKU — because with each pregnancy, there’s a 25% chance of having a child with the condition. If I have children, they will likely be carriers, since they’ll inherit the gene from me.

Despite its lifelong impact, PKU is still considered an orphan disease — many people have never heard of it unless it’s part of their life. That’s why I advocate and educate at every opportunity. Awareness is key to building support and improving care.

Treatments Are Evolving — But Not Accessible Enough
In recent years, new treatments have emerged, including medications like Kuvan (sapropterin) and Palynziq (pegvaliase), which can help some people tolerate more protein by either enhancing enzyme activity or breaking down excess Phe. These treatments are approved in many countries, including Canada, but access is limited and not everyone responds to them.

We need government support to improve access to these treatments and invest in further research. PKU isn’t just a childhood condition — it affects people throughout their lives.

Being an Adult with PKU
Most of the focus is on kids with PKU — which is important — but adults are often forgotten. As a child, you have help from parents, structure, and supervision. But when you grow up, managing PKU becomes a solo responsibility — and it’s hard.

When I was 13, I started cheating on my diet. I stopped drinking my formula, stopped tracking my intake, and started eating more high-Phe foods like potatoes, higher-protein vegetables, starches, and rice. I never ate meat, eggs, dairy, or seafood, but I still felt the effects. My Phe levels soared. I struggled with side effects, and no one understood why.

This story is common — especially for adults who were told in the 1960s and ’70s that they could go off diet after age 7. We now know that was a mistake. Many of those adults are suffering from serious long-term consequences: depression, anxiety, ADHD, cognitive issues, and difficulty maintaining employment.

We need to support adults trying to return to diet and improve their quality of life. No one with PKU should feel forgotten — whether they’re newly diagnosed babies, teens trying to fit in, or adults who are still navigating the challenges of this condition.

Thank You
Thank you for reading and for supporting the PKU community. By sharing this information, you help raise awareness — and awareness is the first step toward change.

Please help me spread the word and make PKU a known disease.

With love and determination,
Amanda Horner