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Cerebrospinal Fluid (CSF) Substance Concentration of Citrulline

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of citrulline, an amino acid, in your cerebrospinal fluid (the fluid surrounding your brain and spinal cord). It may be used to evaluate conditions affecting the central nervous system.

Quick summary

["Citrulline in CSF can help diagnose or monitor certain neurological disorders."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
22654-8
Short code
Citrulline CSF-sCnc
Synonyms
Citrulline CSF-sCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like headaches, seizures, or neurological issues that suggest conditions such as urea cycle disorders, metabolic imbalances, or other CNS-related problems. It may also be part of a broader evaluation for suspected inborn errors of metabolism.

What to Expect Before the Test

No special preparation is typically required. You may be asked to fast for a few hours before the test, but this depends on your provider’s instructions. You’ll have a small needle inserted into your spinal column to collect the CSF fluid.

What Happens During the Test

The test involves a lumbar puncture (spinal tap), where a needle is guided into your lower back to collect CSF. The fluid is then sent to the lab for analysis. This procedure usually takes about 15–30 minutes and may cause mild discomfort.

What the Results Mean

Results are interpreted by your healthcare provider based on your clinical picture. Abnormal levels may indicate metabolic disorders, infections, or other neurological conditions. No standard reference ranges are provided here; your provider will discuss findings with you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CSF Citrulline Level

Frequently asked questions

What causes abnormal citrulline levels in CSF?
Abnormal levels may result from genetic metabolic disorders (e.g., urea cycle defects), infections, inflammation in the CNS, or other conditions disrupting normal amino acid metabolism. Always discuss symptoms and results with your healthcare provider.
How is this test different from blood citrulline tests?
This test specifically measures citrulline in CSF, while blood tests measure citrulline in whole blood or plasma. CSF levels can reflect brain and spinal cord metabolism differently than blood levels, making this test useful for diagnosing CNS-specific issues.
Can diet affect this test result?
Dietary protein intake may influence blood citrulline levels, but CSF citrulline is less affected by diet. Your provider may still recommend fasting or specific dietary restrictions depending on your overall health and test context.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy