Summary
| Direction in Long COVID | ↑ Elevated — higher than in the comparison group |
|---|---|
| Category | Coagulation |
| Also described as | Clotting factor |
| Compared against | HC (healthy controls) |
| Associated symptoms | Coagulation activation |
| Test type | Blood test (serum / plasma / whole blood) |
| LOINC code | 3255-7 |
| Source | Thomas et al. 2024 — doi:10.1007/s40291-024-00731-z |
| Condition atlas | Long COVID Biomarker Atlas |
Other conditions where Fibrinogen is reported
- Fibrinogen in COPD — ↑ elevated vs smokers/COPD vs non-smokers
See the cross-condition hub: Fibrinogen across conditions.
Trials, interventions and tests
In clinical-trial registrations this marker maps to the outcome term Fibrinogen (5 registered trials use a matching outcome measure).
Clinical trials using Fibrinogen as an outcome
- NCT06766825: Study to Evaluate the Efficacy and Safety of Plitidepsin in Adults With Post-COVID-19 Condition (PCC) (Recruiting)
Outcome measure: To compare alterations in thromboinflammatory components (Fibrinogen), among the three treatment arms. - NCT05877508: Anti-SARS-CoV-2 Monoclonal Antibodies for Long COVID (COVID-19) (Active Not Recruiting)
Outcome measure: Fibrinogen - NCT05035628: Cardiopulmonary Rehabilitation in Long COVID-19 Patients With Persistent Breathlessness and Fatigue (Completed)
Outcome measure: Change in markers of coagulation - NCT06065033: Exercise Interventions in Post-acute Sequelae of Covid-19 (Withdrawn)
Outcome measure: Fibrinogen - NCT05669261: Treatment of Long COVID Symptoms Utilizing Autologous Stem Cells Following COVID-19 Infection (Unknown)
Outcome measure: Assessment of Change in Fibrinogen (Coagulation factors II) Laboratory Testing Results
Interventions studied alongside this marker
Hypothesis-generating links from trial outcome usage and literature co-occurrence. Not treatment recommendations.
- Exercise therapy — 2 trials, 6 PubMed co-citations
e.g. Exploring Coagulation Abnormalities and Functional Impairment in Long COVID: Relevance to Primary Care…
Commercial test availability
Fibrinogen — commercial laboratory test.
Links are for reference only; availability, specimen requirements and coverage vary by location.
Related Coagulation markers in Long COVID
- D-dimer ↑
- PAI-1 ↑
- Amyloid-fibrin microclots ↑
- Platelet hyperactivation ↑
- Thrombin-antithrombin complex ↑
Full list: Long COVID Biomarker Atlas.
Frequently asked questions
Is Fibrinogen high or low in Long COVID?
Elevated. Studies summarised in the OSMF atlas report higher Fibrinogen in Long COVID than in healthy controls. Source: Thomas et al. 2024.
What symptoms is Fibrinogen associated with in Long COVID?
The cited literature associates this marker with Coagulation activation. These are population-level associations and do not mean the marker causes the symptoms.
Which test measures Fibrinogen?
It is measured as a blood test (serum / plasma / whole blood). The standard laboratory code is LOINC 3255-7. Commercial laboratories such as Quest Diagnostics, LabCorp list an orderable assay.
Is one abnormal Fibrinogen result diagnostic of Long COVID?
No. No single biomarker is diagnostic of Long COVID. Fibrinogen 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.
Is Fibrinogen specific to Long COVID?
No. The same marker is also reported in COPD in this atlas, so it reflects shared biology (for example inflammation or vascular stress) rather than a condition-specific signature.
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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.