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Home > Vitafriendspku > Your pku journey > Impact of High Phe Levels

Impact of High Phe Levels


In the teenage years, it remains important to follow your low protein diet to control your blood phe levels. You may have started to take more control of your own diet which you will need to embrace alongside other changes in your life such as starting school or new hobbies. Becoming a teenager brings about many changes to your body and mind, growth spurts, increased physical activity and changes to hormones. This can all have an effect on your blood phe and it may be necessary for more blood spot monitoring during this time. Despite these challenges, it is essential that you consume a healthy balanced PKU diet, which includes enough energy and nutrients to grow, be active and generally be the best version of you! There are lots of benefits for you in following the diet, one of which is keeping your blood phe levels in the correct range. In this section, the potential impact of high phe levels – both short- and long-term shall be looked at.

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Some teenagers find they suffer with headaches and a feeling of ‘brain fog’ if their phe levels are high. High phe levels may have a negative effect on mood and attention span. You may feel a bit muddled and your friends and family may notice you’re not quite yourself. This could also lead to you struggling at school and not performing to your best in exams.  

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It has been shown that it is unsafe to stop treatment in childhood and pre-adolescence. There is a lot of uncertainty over the long-term effects of high phe levels in teenagers and adults. The oldest individuals to be diagnosed through newborn screening are now in their 50s and the impact of high levels of phe on ageing are not known.  As there is currently no strong evidence that it is safe to discontinue dietary management in adults, the experts recommend diet for life. 


Possible long-term risks associated with high phe levels may include: 


  • depression and anxiety 

  • tremors (the shakes) 

  • stiff or weak legs 

  • headaches 

  • eczema 

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Additional concerns
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High phe levels do not tend to occur in isolation. If an individual has high phe levels due to no longer taking their protein substitute as part of their diet, they are also at risk of multiple nutritional deficiencies. If somebody simply stops taking their protein substitute whilst remaining on a severely restricted protein intake, they are putting themselves at risk of not having enough protein, vitamins and minerals.  

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