Health Topic

Phenylketonuria

In phenylketonuria (PKU), your body can't process phenylalanine, an amino acid in most foods. Read about genetics, screening, and special diets.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: PKU

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Phenylketonuria

Phenylketonuria (PKU) is a type of amino acid metabolism disorder. It is inherited. If you have it, your body can't process phenylalanine (Phe). Phe is an amino acid, a building block of proteins. It is in almost all foods. If your Phe level gets too high, it can damage your brain and cause severe intellectual disability. All babies born in U.S. hospitals must now have a screening test for PKU. This makes it easier to diagnose and treat the problem early.

The best treatment for PKU is a diet of low-protein foods. There are special formulas for newborns. For older children and adults, the diet includes many fruits and vegetables. It also includes some low-protein breads, pastas, and cereals. Nutritional formulas provide the vitamins and minerals you can't get from their food.

Babies who get on this special diet soon after they are born develop normally. Many have no symptoms of PKU. It is important to stay on the diet for the rest of your life.

It sits within Brain and Nerves, Genetics/Birth Defects and Metabolic Problems.

The lead U.S. institute for this subject is the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Phenylketonuria

194 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Symptoms

Diagnosis and Tests

Treatments and Therapies

Related Issues

Genetics

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Phenylketonurias. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Phenylketonuria, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.