|Cause of low blood phenylalanine levels||Action|
|Inadequate intake of natural protein||
• Ensure all prescribed intake of natural protein/phenylalanine is eaten.|
• Check understanding of exchange system/phenylalanine content of foods.
• Re-educate as necessary.
|Anabolic phase, following an intercurrent infection||
• Ensure all prescribed intake of natural protein is eaten.|
• Repeat blood phenylalanine level, and if is still low, consider an increase of natural protein by approx. 0.5-1 g protein or 25 to 50 mg/day phenylalanine but monitor blood phenylalanine levels carefully.
|Rapid growth spurt such as puberty||
• Increase natural protein by 0.5-1 g/day protein or phenylalanine by 25 to 50 mg/day if blood phenylalanine levels are consistently below target range.|
• Increase by a further 0.5 to 1 g/day protein or phenylalanine by 25 to 50 mg/day for every 3 consecutive blood phenylalanine levels below target range.
|Excess intake of infant protein substitute or overnight consumption of infant protein substitute.||• Infants may take phenylalanine- free infant protein substitute overnight, which may lower morning blood concentrations. Consider reducing overnight intake if appropriate.|
|No obvious reason||
• Consider increasing natural protein by approx. 0.5-1 g protein or phenylalanine by 25 to 50 mg/day.|
• Monitor blood phenylalanine levels carefully.
• It is good practice to re-check blood phenylalanine levels before any further increase in natural protein /phenylalanine intake.