Indicator Explainer
Phenylalanine
An essential aromatic amino acid in humans (provided by food), Phenylalanine plays a key role in the biosynthesis of other amino acids and is important in the structure and function of many proteins and enzymes. Phenylalanine is converted to tyrosine, used in the biosynthesis of dopamine and norepinephrine neurotransmitters. The L-form of Phenylalanine is incorporated into proteins, while the D-form acts as a painkiller. Absorption of ultraviolet radiation by Phenylalanine is used to quantify protein amounts. (NCI04)
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C29601. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-20. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also Known As
References
- NCI Thesaurus 26.09d — Phenylalanine (C29601)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C29601. NCI definition, reproduced without modification under CC BY 4.0.
- Developing phenylalanine decaging. — Nat Chem Biol, 2026-10-19 (PMID 42897257; literature)
- Phenylalanine-driven metabolic induced resistance activates phenylpropanoid defenses in tomato against Tetranychus urticae. — Plant Sci, 2026-10-14 (PMID 42874803; literature)
- Influence of ultraviolet/chlor(am)ine processes on the formation of toxicity and aromatic byproduct from the dipeptide tyrosyl-L-phenylalanine. — J Hazard Mater, 2026-10-21 (PMID 42914919; literature)
- Unraveling the proteome of Escherichia coli during L-phenylalanine production in a scale-down bioreactor. — Metab Eng, 2026-10-21 (PMID 42906772; literature)