Summary
| Direction in Long COVID | ↓ Reduced — lower than in the comparison group |
|---|---|
| Category | Metabolic |
| Also described as | Amino acid |
| Compared against | HC (healthy controls) |
| Associated symptoms | NO pathway, immune function |
| Test type | Blood test (serum / plasma / whole blood) |
| Source | Saito et al. 2024 — doi:10.3389/fimmu.2024.1341843 |
| Condition atlas | Long COVID Biomarker Atlas |
Trials, interventions and tests
In clinical-trial registrations this marker maps to the outcome term Neuropeptide Y (1 registered trials use a matching outcome measure).
Clinical trials using Arginine as an outcome
- NCT03496961: Yan Nian Jiu Zhuan Fa Improve Chronic Fatigue Syndromes (Unknown)
Outcome measure: Neuropeptide Y
Also sold as a nutrient or supplement
L-Arginine (amino acid). Nitric oxide precursor; widely sold OTC. This tag means the analyte is also available orally; it is not a product endorsement and a low or high level does not by itself justify supplementation.
Related Metabolic markers in Long COVID
- Glutamine ↓
- Histidine ↓
- Asparagine ↓
- TCA cycle intermediates ↑
- Aspartate ↓
- Kynurenine ↑
- Sarcosine ↓
- 5-Hydroxykynurenine ↑
Full list: Long COVID Biomarker Atlas.
Frequently asked questions
Is Arginine high or low in Long COVID?
Reduced. Studies summarised in the OSMF atlas report lower Arginine in Long COVID than in healthy controls. Source: Saito et al. 2024.
What symptoms is Arginine associated with in Long COVID?
The cited literature associates this marker with NO pathway, immune function. These are population-level associations and do not mean the marker causes the symptoms.
Which test measures Arginine?
It is measured as a blood test (serum / plasma / whole blood). Many of the cited studies used research-grade assays, so clinical availability may vary.
Is one abnormal Arginine result diagnostic of Long COVID?
No. No single biomarker is diagnostic of Long COVID. Arginine findings come from group comparisons, overlap considerably between patients and controls, and vary with study design, timing and comparison group. A result should be interpreted by a clinician alongside symptoms, history and other tests.
Cite this page
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Last reviewed: 2026-06-29 · Page generated from long-covid.json · Browse: Long COVID atlas · Biomarker Index · All marker pages
Disclaimer: This page is an educational synthesis of published, peer-reviewed research and is not medical advice. Biomarker findings vary across studies with case definitions, comparison groups, timing and assay methods. Direction of change reflects the predominant finding in the cited source and does not establish a diagnostic threshold. Discuss any test result with a qualified clinician.