Updated on December 16, 2025.
Phenylketonuria (PKU) is a rare genetic disorder that can lead to a toxic buildup of an amino acid called phenylalanine. Phenylalanine is found in proteins. People who have PKU have genetic mutations that disrupt the body’s normal production of an enzyme needed to metabolize this amino acid.
Newborns in the United States are typically screened for PKU shortly after birth. This allows treatment to begin as early as possible. However, some people are diagnosed later in life.
What healthcare providers treat PKU?
It’s recommended that treatment for PKU take place at a clinic that specializes in the care of metabolic disorders like PKU. This may be a part of a clinical genetics center, and genetic counseling is often a part of treatment.
Key members of a healthcare team include a metabolic physician and metabolic dietitian. Other members of a healthcare team can include a pediatrician, genetics counselor, developmental specialists, mental health professional, and social worker.
What do I need to ask my child’s healthcare team?
Treatment for PKU will depend on the type and severity of the disease, the genetic mutations involved, and other factors. These questions can be helpful to answer when a child is starting treatment for PKU.
What foods need to be avoided?
Diet is the main treatment for all types of PKU. People with PKU will need to follow a diet that restricts foods containing phenylalanine. This includes meat, poultry, fish, eggs, dairy products, nuts, beans, breads, and any foods containing an artificial sweetener called aspartame. Certain vegetables and grains will also need to be limited. How much these foods need to be restricted can vary from person to person. Ask your healthcare team for clear and specific guidelines on what foods to avoid and limit.
What foods can my child eat?
Good nutrition is essential to growth, development, and health. Ask your healthcare team for clear and specific instructions on the foods your child should be eating. Newborns and infants will require formula that provides protein without phenylalanine. Older children, adolescents, and adults will also require phenylalanine-free nutritional supplements.
How will phenylalanine levels be monitored?
Children with PKU need regular blood tests to monitor phenylalanine levels. Ask your child’s healthcare team for a schedule for testing, what test results mean, and what you can expect when you go in for a test.
Will my child need medications?
There are also several medications that may be prescribed to help lower phenylalanine levels in children that are 1 month or older. These medications can be used alongside diet. To determine if these medications are an appropriate treatment option, a healthcare team may perform something called a loading test. During a loading test, a person will take a medication for a period of time. Bloodwork will be used to measure phenylalanine levels and check for a response.
How will we monitor growth and development?
PKU, especially when untreated or inadequately treated, can cause cognitive disability, developmental delays, behavioral problems, and other complications. Treatment can prevent these complications, but monitoring for growth and developmental milestones will be an important part of treatment, and this is another important topic to discuss with a healthcare team.
Who do I contact when I have a question?
Know how to reach your healthcare providers when you have a question or a concern—including a question or concern that is urgent.
Where can I go for support?
Being a parent or caregiver for a child with a condition like PKU is challenging. There is a need for social support, counseling, financial assistance, and patient/caregiver education. Talk to your child’s healthcare team about your specific challenges and concerns and ask what resources are available.
