Long COVID is linked to inflammation that lingers, but no one has shown it drives the symptoms. A 2024 meta-analysis of 103 studies found higher CRP and 21 other immune signals in people with long COVID. Yet two trials of drugs that calm inflammation did not improve their main goals.
Eight months later, still switched on
In 2022, a research team studied people who still had symptoms more than 12 weeks after a mild or moderate COVID infection. They compared them with people of the same age and gender who had recovered fully.
The people with long COVID had immune cells that were still highly active. They were short on fresh, unused T and B cells, the immune cells that learn to fight new germs. And some of their virus-fighting signals, called interferons, stayed high 8 months after infection. A small set of these signals, IL-6 among them, could pick out who had long COVID 78.5% to 81.6% of the time.
That was an early clue. Since then, dozens of teams have gone looking for the same thing.
First, a quick definition. Long COVID means symptoms that last weeks to months after the infection itself is over. It follows at least 1 in 10 infections, by one major 2023 review, and more than 200 symptoms have been tied to it, across many parts of the body.
Does long COVID cause inflammation? What blood studies show
A meta-analysis pools the results of many studies, so it can spot a pattern a single study might miss.
Colchicine, an anti-inflammatory drug, did not improve walking, breathing or inflammation markers in 346 adults with long COVID.From a 2025 randomized trial in JAMA Intern Med
The largest, from 2024, pulled together 103 studies. It compared 5,502 people with long COVID against 5,962 people without it. CRP (C-reactive protein, a common blood test for inflammation) and 21 different immune signals were higher in the long COVID group.
A 2026 meta-analysis of 33 studies, with 3,294 patients, asked how long it lasts. It compared people who had COVID and then developed long COVID with people who had COVID and recovered. IL-6, TNF-alpha and two other signals were higher in long COVID, both within the first 6 months and after it. Its authors read this as a sign that symptoms may have an inflammatory basis.
IL-6 has the most data on its own. Across 22 studies, people with long COVID averaged 9.75 pg/ml more IL-6 than healthy people, and 3.32 pg/ml more than people who had COVID without lasting symptoms. That second gap matters most, because it compares people who all had the same infection.
The catch: an uneven blood picture
A 2023 review of 23 studies checked 24 different blood markers. CRP, D-dimer and white blood cell counts were higher in people with long COVID than in people who recovered. But many others, including ferritin, platelets and fibrinogen, showed no clear difference.
The review also found that the changes were mostly driven by people whose long COVID was diagnosed from a problem in an organ, not by symptoms alone. They were also stronger in cases under 6 months old. So a person with months of fatigue and normal organ tests may not have the blood picture these reviews describe.
The IL-6 studies also disagreed sharply on the size of the gap: a measure of how much results varied hit 100%, the top of the scale. And all of this is from studies that look at people at one point in time. They can show that inflammation and long COVID travel together. They cannot show which one comes first.
If inflammation is the driver, why didn't the drugs help?
This is the test that matters. If lingering inflammation were the main engine of long COVID, turning it down should help. A 2025 randomized trial checked. Researchers gave 346 adults with long COVID either colchicine, an established anti-inflammatory drug, or a dummy pill for 26 weeks. At 52 weeks, the colchicine group walked no farther in a 6-minute walk test than the placebo group. Colchicine did not improve breathing tests or inflammation markers either.
A 2026 trial tried a different pair of drugs, losartan and prednisolone, in 279 people with long COVID and signs of heart inflammation on scans. After 16 weeks, the main measure of heart pumping was neutral. Some symptom scores leaned toward the drugs, but the results could have been chance.
Neither trial closes the case. Inflammation may matter for some people and not others, or it may be one piece of a bigger puzzle. A 2023 review of the field said current treatments are insufficient and called for trials that test the leading ideas.
What this means for you
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your symptoms get worse for a day or more after physical or mental effort; you have chest pain, a racing heart when you stand, or new shortness of breath; you are thinking about taking a drug or supplement for long COVID; or you already take medicine for your heart, lungs or immune system.
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The bottom line
Eight months after a mild infection, some immune signals were still high. Across 103 studies, CRP and 21 other signals ran higher. Then two careful trials turned inflammation down, or tried to, and people did not get measurably better. Put together, the evidence says inflammation is part of the long COVID story, not the whole plot. That is less satisfying than a single villain. It is also more honest, and it points to what helps today: a careful, guided return to activity, and a doctor who looks at every symptom.
Common questions
Is long COVID a chronic inflammatory disease?
It is not classed that way yet. Many studies link long COVID to higher inflammation markers that can last past 6 months. But the gap is uneven: in one review it came mostly from people with organ problems. And an anti-inflammatory drug did not improve walking, breathing or inflammation markers in a 2025 trial.
Is there an anti-inflammatory diet for long COVID?
Not one backed by trials in our sources. None of the 10 papers we used tested a diet for long COVID. A 2023 review of the field said treatment options are still insufficient and that trials must be a priority. Until diet trials report, any long COVID diet plan is a guess, however well meant.
Does long COVID cause inflammation in the brain?
It may, but the proof is thin. A 2026 review of 42 studies found changes in brain activity and structure in people with long COVID, and some studies found markers suggestive of brain inflammation. These changes were often tied to fatigue and brain fog. The authors said the studies varied widely and that firm conclusions are not possible yet.
Does long COVID inflammation go away?
For some markers, not quickly. In a 2026 meta-analysis of 33 studies, IL-6, TNF-alpha and two other signals were still higher after 6 months. One 2022 study found some immune signals high 8 months after a mild or moderate infection. Studies that follow the same people for years are still needed.
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How this article was made
Researched and written from 10 peer-reviewed papers. Our automated check matched every claim against the exact words of its source, confirmed every paper exists in PubMed, and found none retracted. Checked November 1, 2026. Not individually reviewed by a doctor. Photos are illustrative; the people in them are not patients or readers.
Grades run Strong, Moderate, Emerging, Early and Not supported, and the grade decides the words we may use. How we grade evidence · Medical disclaimer
Sources
- Meta-analysisPersistent inflammatory cytokine signature in long Covid-19 patients: a meta-analysis.Dornas W, Reis JP, Belilo TE et al. Inflammopharmacology, 2026.PubMedFull paper
- Meta-analysisIncreased interleukin-6 is associated with long COVID-19: a systematic review and meta-analysis.Yin JX, Agbana YL, Sun ZS et al. Infect Dis Poverty, 2023.PubMedFull paper
- Meta-analysisInflammatory and vascular biomarkers in post-COVID-19 syndrome: A systematic review and meta-analysis of over 20 biomarkers.Yong SJ, Halim A, Halim M et al. Rev Med Virol, 2023.PubMedFull paper
- Meta-analysisImmune activation and immune-associated neurotoxicity in Long-COVID: A systematic review and meta-analysis of 103 studies comprising 58 cytokines/chemokines/growth factors.Almulla AF, Thipakorn Y, Zhou B et al. Brain Behav Immun, 2024.PubMedFull paper
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- CohortImmunological dysfunction persists for 8 months following initial mild-to-moderate SARS-CoV-2 infection.Phetsouphanh C, Darley DR, Wilson DB et al. Nat Immunol, 2022.PubMedFull paper
- Randomized trialEffectiveness of Colchicine for the Treatment of Long COVID: A Randomized Clinical Trial.Bassi A, Devasenapathy N, Thankachen SS et al. JAMA Intern Med, 2025.PubMedFull paper
- Randomized trialLosartan and prednisolone for post-COVID syndrome and cardiac inflammation: a randomized, double-blind, placebo-controlled trial.Puntmann VO, Nagel E, Beitzke D et al. Nat Commun, 2026.PubMedFull paper
- Systematic reviewCentral Nervous System Alterations in Individuals with Long COVID: A Systematic Review.Moraes JF, Souza PHL, Andrade ML et al. Rev Soc Bras Med Trop, 2026.PubMedFull paper
- Meta-analysisEffect of pulmonary rehabilitation for patients with long COVID-19: a systematic review and meta-analysis of randomized controlled trials.Li S, Dai B, Hou Y et al. Ther Adv Respir Dis, 2025.PubMedFull paper
