Citrulline

An amino acid involved in the urea cycle and nitric-oxide production.

Last reviewedJune 16, 2026

Plasma

sample type

~5 mL

blood needed

~7 days

results in app

Morning, fasting

best timing

INCLUDED WITH ANIVA

199 € / year

0.55 € a day

Get Started

100+ biomarkers. Cheaper than a comparable test at your doctor. Guaranteed, or we match the price.

German PKV insurance usually reimburses.

On this page

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

In short

Citrulline is an amino acid that the body does not use to build proteins. It is made mainly in the gut lining and takes a central part in the urea cycle, the pathway that clears ammonia. It is also a stepping stone in the body's production of arginine and nitric oxide.

Comprehensive Health Check

Reviewed against DGKL reference practice.

Why test this?

It is measured as part of a plasma amino acid profile. Levels give insight into the urea cycle and into how well the small intestine is working, since most citrulline is made there. Unusual readings can point to urea cycle disorders or reduced gut function and are interpreted alongside the rest of the panel.

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.

Group	Adult fasting plasma range
Adults	10 to 45 µmol/L

Amino acid ranges vary by laboratory and method. They are best read as part of the full plasma amino acid profile, not in isolation.

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?

Insight into the urea cycle and ammonia handling.
An indirect marker of small intestine function.
A possible signal of urea cycle patterns if clearly abnormal.

What can affect this result?

What can skew the result

Recent protein intake, citrulline supplements, fasting state, and time of day affect the result. A fasting morning sample gives the most reliable reading.

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
MedlinePlus: Plasma 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.