Isoleucine

An essential branched-chain amino acid that supports muscle and energy.

Last reviewedJune 16, 2026

Plasma

sample type

~5 mL

blood needed

~7 days

results in app

Morning, fasting

best timing

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

In short

Isoleucine is an essential amino acid and one of the three branched-chain amino acids, alongside leucine and valine. Your body cannot make it, so it comes from protein in food. It supports muscle protein, energy production and blood sugar handling.

Comprehensive Health Check

Reviewed against DGKL reference practice.

Why test this?

Plasma isoleucine is part of a full amino acid profile and reflects protein intake and how your body handles the branched-chain amino acids. Low levels can reflect poor intake, while high levels are seen in some inherited metabolic conditions such as maple syrup urine disease. It is most useful read with leucine and valine.

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 reference values as used by Aniva. Ranges are guidance and can vary by laboratory and method.

Group	Normal range
Adults	36 to 107 µmol/L

Sources: 2019 ARUP Plasma Amino Acids, Mayo Clinic Laboratories: Amino Acids, Quantitative, Plasma

Your Aniva report reads your result against these values together with your age, sex and the rest of your panel.

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 isoleucine sits in the usual adult fasting range.
How it compares with the other branched-chain amino acids, leucine and valine.
A piece of the picture of how your body handles dietary protein.

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: Biochemistry, Essential Amino Acids

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.