Targeted Metabolomics Services


Updated 21/12/2022

What is citrulline?

Citrulline is a non-essential α-amino acid, part of the urea cycle, and linked to the metabolism arginine, ornithine, aspartate and production of nitric oxide (2). It is associated with several diseases, including Alzheimer’s disease, rheumatoid arthritis, inflammatory bowel disease (IBD) and some inborn errors of metabolism. Pathogenic effects may involve post-translational protein modification by citrullination (2,3).
Method: LC-MS/MS.


Should be measured together with arginine and ornithine.

Specimen, collection and processing

Matrix: EDTA plasma and serum.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: The blood sample must be centrifuged and the plasma/serum fraction put on ice, and frozen.


Frozen, on dry ice. (for general instruction on transportation, click here)

Reported values, interpretation

Reported values: 10-60 µmol/L
Intraclass correlation coefficient (ICC): NA.


1. Midttun, O., Kvalheim, G., and Ueland, P.M. (2013). High-throughput, low-volume, multianalyte quantification of plasma metabolites related to one-carbon metabolism using HPLC-MS/MS. Anal Bioanal Chem 405, 2009-017.
2. Curis, E., Nicolis, I., Moinard, C., Osowska, S., Zerrouk, N., Bénazeth, S. et al. (2005). Almost all about citrulline in mammals. Amino Acids, 29, 177-205.
3. Papadia, C., Osowska, S., Cynober, L., and Forbes, A. (2018). Citrulline in health and disease. Review on human studies. Clin Nutr, 37, 1823-1828.

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