What is Phenyllactic acid? High and low values | Lab results explained

Phenyllactic acid is a metabolite of phenylalanine.

Inborn errors of metabolism are genetic disorders that disrupt biochemical pathways in the body. These disorders are rare, but their effects can be devastating. Often, there is a defect in a gene that codes for a certain enzyme, causing the body to either produce malfunctioning enzymes or none of the enzymes at all. These missing or malfunctioning enzymes prevent important biochemical reactions from occurring and cause metabolites (including organic acids) to accumulate. For example, one of the better known inborn errors of metabolism is phenylketonuria (PKU). In PKU, there is a defect in the gene for phenylalanine hydroxylase (PAH), which is responsible for converting the amino acid phenylalanine to tyrosine. When PAH isn’t working properly, the body tries to metabolize phenylalanine through an alternative pathway, and organic acids like phenyllactate and phenylacetate are produced as a result.



– Slight elevations may result from increased dietary intake of phenylalanine.
– Moderate amounts of phenyllactic acid may be due to gastrointestinal overgrowth of the intestine of the following Clostridia bacteria: C. sordellii, C. stricklandii, C. mangenoti, C. ghoni, and C. bifermentans. C sordellii is usually considered a nonpathogen except in immunocompromised people, but has been implicated in catastrophic infectious gynecologic illnesses among women of childbearing age. The other species have rarely or never been reported to be pathogenic.
– Elevated values indicate increased intake of dietary phenylalanine, or the heterozygous carrier status or homozygosity for the genetic disease phenylketonuria (PKU). 
– Values observed in clinically diagnosed PKU typically exceed 200 mmol/mol creatinine.
– Elevated in tyrosinemia.


Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

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