Phenylalanine

An essential amino acid and precursor to tyrosine and neurotransmitters.

Last reviewedJune 16, 2026

Plasma

sample type

~5 mL

blood needed

~7 days

results in app

Morning, fasting

best timing

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On this page

Why test Reference ranges What you'll learn What affects it How testing works Sources FAQ

In short

Phenylalanine is an essential amino acid that comes from food. It is a building block for proteins and the source of tyrosine, which in turn makes dopamine, adrenaline and thyroid hormones. Your body converts most surplus phenylalanine into tyrosine.

Comprehensive Health Check

Reviewed against DGKL reference practice.

Why test this?

Plasma phenylalanine is part of a full amino acid profile. The best known reason to measure it is phenylketonuria, an inherited condition where phenylalanine builds up. Raised levels are read together with tyrosine and the rest of the profile.

What is a normal result?

Aniva reads your result against research-backed ranges, not just the lab's wide normal. The reference shown below is specific to this biomarker.

Adult fasting plasma, guidance only:

Analyte	Typical adult range (µmol/L)
Phenylalanine	40 to 85

Ranges vary by laboratory and assay and are read as part of the full amino acid profile.

Ranges are guidance and vary by lab and assay, aligned with DGKL practice. Always read your result against your own lab's reference interval.

What insights will this test give you?

Whether phenylalanine sits in the usual adult fasting range.
How it compares with tyrosine, the amino acid it converts into.
In some cases, a clue that supports a closer look at an inherited metabolic pattern.

What can affect this result?

What can skew the result

Results are affected by recent diet, recent protein intake, fasting state and the time of day the sample is taken.

Best interpreted with

Read as part of the full plasma amino acid profile.

How is this tested?

Sample

Plasma

Blood needed

~5 mL

Method

Ion-exchange chromatography or LC-MS/MS

Best timing

Morning, fasting

Sources. The evidence behind this

Mayo Clinic Laboratories: Amino Acids, Quantitative, Plasma
StatPearls: Phenylketonuria

Common questions

Which Aniva panels include this marker?

Amino Acids

These tests assess essential, non-essential, and branched-chain amino acids, plus related metabolites and functional ratios.