Summary
| Direction in Long COVID | ↑ Elevated — higher than in the comparison group |
|---|---|
| Category | Metabolic |
| Also described as | Succinate, citrate, etc. |
| Compared against | R (fully recovered) (recovered individuals without persistent symptoms (fully recovered)) |
| Associated symptoms | Mitochondrial dysfunction |
| Test type | Blood test (serum / plasma / whole blood) |
| Source | Pérez-Mazliah et al. 2024 — doi:10.1021/acs.jproteome.3c00706 |
| Condition atlas | Long COVID Biomarker Atlas |
Trials, interventions and tests
In clinical-trial registrations this marker maps to the outcome term Change in 6 Minute Walk Test at the End of Treatment Period (3 registered trials use a matching outcome measure).
Clinical trials using TCA cycle intermediates as an outcome
- NCT05096884: Post-Acute Sequelae of Coronavirus-19 (COVID-19) With Dyspnea on Exertion And Associated TaChycardia TrEatment Study (Terminated)
Outcome measure: Change in 6 Minute Walk Test at the End of Treatment Period - NCT05890534: Pycnogenol® in Post-COVID-19 Condition (Completed)
Outcome measure: D-Dimer - NCT05531019: COVID-19 Sequelae: Treatment and Monitoring. A Dietary Supplement Based on Sea Urchin Eggs With Echinochroma A (Completed)
Outcome measure: Change of D Dimer over time-points (baseline, 4 weeks, 12 weeks, 12 weeks) via blood sample.
Related Metabolic markers in Long COVID
- Histidine ↓
- Kynurenine ↑
- Arginine ↓
- 5-Hydroxykynurenine ↑
- Glutamine ↓
- Serotonin ↑
- Asparagine ↓
- Putrescine ↑
Full list: Long COVID Biomarker Atlas.
Frequently asked questions
Is TCA cycle intermediates high or low in Long COVID?
Elevated. Studies summarised in the OSMF atlas report higher TCA cycle intermediates in Long COVID than in recovered individuals without persistent symptoms (fully recovered). Source: Pérez-Mazliah et al. 2024.
What symptoms is TCA cycle intermediates associated with in Long COVID?
The cited literature associates this marker with Mitochondrial dysfunction. These are population-level associations and do not mean the marker causes the symptoms.
Which test measures TCA cycle intermediates?
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 TCA cycle intermediates result diagnostic of Long COVID?
No. No single biomarker is diagnostic of Long COVID. TCA cycle intermediates 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
Subscribe on Substack
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.