How to Deal With Fatigue When You Have Phenylketonuria

How to Deal With Fatigue When You Have Phenylketonuria

High or unstable blood phenylalanine levels can lead to symptoms of fatigue in adults with phenylketonuria (PKU). If you have PKU, here are tips on how to cope.

What is PKU?

PKU is a rare genetic metabolic disorder characterized by the buildup of phenylalanine, an amino acid or protein building block. Phenylalanine is found in protein foods and some artificial sweeteners.

In people with PKU, the enzyme that processes phenylalanine does not work properly. That’s why patients need to adhere to a lifelong low-protein diet. While adhering to such a restrictive nutrition plan can be demanding, compliance staves off symptoms that, depending on the disease type, can include fatigue, seizures, eczema, hyperactivity, intellectual disability, psychiatric disorders, and behavioral problems.

Is fatigue an issue in PKU?

While it is not a characteristic symptom of phenylketonuria, many patients report fatigue as an issue.

For example, in a survey that aimed to characterize the dietary habits of adult PKU patients and identify psychological factors influencing disease perception and adherence to diet, 25% of respondents said they experienced fatigue often, meaning at least twice a week, and even daily.

Another study examining neuropsychiatric diagnoses in the PKU population found that rates of fatigue or malaise exceeded those for the general population, and were comparable to individuals who have diabetes, a chronic disorder that also includes dietary intake restrictions and frequent blood monitoring for routine management.

A randomized double-blind placebo-controlled study investigated the effect of short-term elevation of phenylalanine levels on mood and neuropsychological functions in adults with PKU. In a post-study questionnaire, patients reported more fatigue during phenylalanine loading — ingesting capsules containing natural protein — compared to those taking placebo.

How do I deal with fatigue?

Fatigue is considered chronic if it’s been present for more than six months and cannot be relieved with rest. Because feelings of fatigue can be subjective and difficult to quantify or treat, clinicians sometimes disregard it.

Chronic fatigue is burdensome, however, and affects quality of life. You and your physician should discuss the possible causes of fatigue and its impact, and stages of management. Other possible ways to alleviate it include:

Pacing yourself

Conserve your energy and pace yourself, making sure you get enough rest between activities.

Using relaxation techniques

Common relaxation techniques may help in fatigue management. They include progressive muscle relaxation, meditation, yoga, and music and art therapy.

Making lifestyle changes

Research has shown a correlation between fatigue and reduced adherence to a low-protein diet. Therefore, keeping phenylalanine levels within range could provide you some relief. Improving overall fitness and sleeping patterns could also help.

In addition, cognitive-behavioral therapy may help you change any unhealthy habits that may cause or add to fatigue.

Avoiding bedtime distractions

Since sleep problems can worsen fatigue, you should avoid watching television, looking at a computer or smartphone screen, and doing anything that might be emotionally upsetting within a few hours of bedtime. Taking a warm bath and reading a book or magazine before bed may be helpful.


Last updated: Sept. 3, 2020


Phenylketonuria News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

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