GLP-1 Medications and Infection Risk: What the Research Shows

Introduction

When a new class of drugs reaches tens of millions of people, one of the first safety questions clinicians ask is deceptively simple: does it change how often patients get sick? For GLP-1 medications, the answer has surprised many. Rather than blunting immune defenses, the accumulating data suggest that GLP-1 receptor agonists (GLP-1 RAs) such as semaglutide, tirzepatide, and liraglutide are associated with fewer serious infections — including pneumonia, sepsis, and severe COVID-19.

That finding runs counter to a common assumption. Obesity and type 2 diabetes both impair immune function and raise infection risk, so a drug that treats those conditions might be expected to help indirectly. But the emerging evidence points to something more specific: GLP-1 signaling appears to modulate the immune system directly, and the infection-related benefits show up faster and larger than weight loss alone can explain.

Evidence: "Across 136 randomized controlled trials enrolling 164,322 participants, GLP-1 receptor agonist treatment was associated with an 11% relative reduction in serious infections (RR 0.89; 95% CI 0.86–0.93), with no heterogeneity across trials." — Han S, et al. Journal of Infection. 2025. DOI: 10.1016/j.jinf.2025.106645

This article examines what the strongest studies actually measured, the biology that plausibly explains the effect, and the practical questions patients raise — from perioperative safety to whether these drugs help during respiratory virus season.

What the Largest Analyses Show

The most rigorous data on GLP-1 medications and infection risk come from pooling randomized trials, which minimizes the confounding that plagues observational research. Two large meta-analyses now anchor the field.

Serious Infections and COVID-19

The 2025 systematic review by Han and colleagues is the largest to date. Drawing on 136 randomized trials and more than 164,000 participants, it found consistent reductions across serious, non-serious, and total infections. The COVID-19 signal was particularly striking.

Evidence: "In 17 trials including 39,286 participants, GLP-1 receptor agonist treatment was associated with a lower risk of serious COVID-19 infection (RR 0.82; 95% CI 0.72–0.92) compared with controls." — Han S, et al. Journal of Infection. 2025. DOI: 10.1016/j.jinf.2025.106645

Notably, the authors reported that greater glycemic control and weight loss were linked to larger reductions in infection risk — but the protective association persisted across organ systems, suggesting the metabolic improvements are only part of the story.

Respiratory Illness and Pneumonia

An earlier meta-analysis focused specifically on the lungs reached a similar conclusion. Respiratory tract infections are the leading infectious cause of hospitalization in people with diabetes, making this a clinically meaningful endpoint.

Evidence: "In a pooled analysis of 28 randomized trials with 77,485 participants, GLP-1 receptor agonists reduced overall respiratory disease risk by 14% (RR 0.86; 95% CI 0.81–0.93), with a parallel trend toward fewer pneumonia cases." — Yu M, et al. Diabetology & Metabolic Syndrome. 2023. DOI: 10.1186/s13098-023-01118-6

The per-drug breakdown was consistent: semaglutide reduced respiratory risk by 18%, dulaglutide by 18%, and liraglutide by 14%. The pneumonia-specific reduction (RR 0.89) approached but did not cross the threshold for statistical significance, a limitation the authors attributed to relatively few adjudicated pneumonia events.

The table below summarizes the headline findings from the major datasets.

Study	Design	Participants	Key infection finding
Han et al. 2025	136 RCTs, meta-analysis	164,322	Serious infections RR 0.89; COVID-19 RR 0.82
Yu et al. 2023	28 RCTs, meta-analysis	77,485	Respiratory disease RR 0.86; pneumonia RR 0.89
Scirica et al. 2024 (SELECT)	RCT (post-hoc)	17,604	Fewer non-cardiovascular and infectious deaths
Kazi et al. 2026	Propensity-matched cohort	46,742	Lower pneumonia, sepsis, and bacteremia rates

The SELECT Trial and Mortality Signal

The clearest individual-trial evidence emerged, unexpectedly, from a cardiovascular outcomes study conducted during the pandemic. The SELECT trial randomized 17,604 adults with obesity and established cardiovascular disease — but without diabetes — to semaglutide 2.4 mg or placebo over a mean of 3.3 years.

Because enrollment overlapped with peak COVID-19 waves, investigators were able to prospectively adjudicate infectious deaths, an opportunity that rarely arises in a controlled trial.

Evidence: "Semaglutide reduced all-cause death by 19% versus placebo, and the lower rate of non-cardiovascular death was driven predominantly by fewer infectious deaths, including fewer COVID-19–related deaths." — Scirica BM, et al. Journal of the American College of Cardiology. 2024. DOI: 10.1016/j.jacc.2024.08.007

Importantly, semaglutide did not reduce the number of people who caught COVID-19 — infection rates were similar between groups — but it reduced the odds that an infection turned fatal. That pattern points toward a drug that tempers the severity of infection rather than preventing exposure, consistent with an effect on the inflammatory response to pathogens rather than on transmission.

How GLP-1 Drugs May Influence Immunity

The observation that GLP-1 RAs lower infection severity more than infection frequency has a plausible biological basis. GLP-1 receptors are not confined to the pancreas and brain — they are expressed on immune cells throughout the body.

Direct Effects on Immune Cells

Macrophages, monocytes, and lymphocytes all carry GLP-1 receptors, giving these drugs a direct line to immune signaling. The dominant effect appears to be a shift away from a hyper-inflammatory state.

Evidence: "GLP-1 receptor agonists modulate immune cell signaling and the NF-κB pathway, promote anti-inflammatory M2 macrophage polarization via STAT3, and attenuate excess cytokine production." — Alharbi SH. Therapeutic Advances in Endocrinology and Metabolism. 2024. DOI: 10.1177/20420188231222367

This matters for infection outcomes because severe illness — whether from bacterial sepsis or viral pneumonia — is often driven less by the pathogen itself than by a dysregulated, overexuberant immune response. By dampening that response, GLP-1 signaling may reduce the collateral tissue damage that turns a manageable infection into a life-threatening one. The same anti-inflammatory machinery underlies the broader systemic inflammation reductions documented with these drugs.

Metabolic Repair

The second pathway is indirect but substantial. Chronically elevated blood glucose impairs neutrophil function, weakens mucosal barriers, and creates a favorable environment for pathogens. By improving glycemic control and driving meaningful weight loss, GLP-1 RAs remove several of the metabolic conditions that predispose people with obesity and diabetes to infection in the first place. The Han meta-analysis found that the infection benefit tracked with the degree of glucose and weight improvement — evidence that this pathway is real, even if it is not the whole picture.

Where the Evidence Is Still Mixed

The story is not uniformly reassuring, and honest interpretation requires naming the caveats.

Gastroparesis and Gastrointestinal Concerns

GLP-1 drugs slow gastric emptying, which has raised theoretical concerns about aspiration and gut-related infections, especially in people who already have delayed motility. A large propensity-matched cohort tackled this question directly in patients with diabetic gastroparesis.

Evidence: "Among 46,742 propensity-matched patients with diabetic gastroparesis, GLP-1 users had lower rates of pneumonia (12.2% vs 13.2%), sepsis (11.1% vs 12.8%), and bacteremia (4.4% vs 5.2%) than non-users." — Kazi MAI, et al. Advances in Respiratory Medicine. 2026. DOI: 10.3390/arm94020020

Even in this higher-risk group, the infectious signal favored GLP-1 therapy — suggesting the metabolic and anti-inflammatory benefits outweighed motility-related concerns. That said, this remains observational data, and delayed emptying is still the reason anesthesiologists ask about GLP-1 use before procedures.

Perioperative and Procedural Context

Slowed gastric emptying is a genuine, if separate, safety issue during surgery and endoscopy, where retained stomach contents raise aspiration risk. This is a mechanical concern rather than an immune one, and it is managed through dosing pauses and airway precautions rather than by stopping the drug outright. Patients scheduled for a procedure should review the specifics in our guide to GLP-1 medications and surgical safety and always disclose their medication to the anesthesia team.

Observational Limits

Most of the encouraging infection data outside of SELECT come from meta-analyses of trials designed for other endpoints, or from cohort studies vulnerable to residual confounding — healthier, more adherent patients are more likely to stay on GLP-1 therapy. A dedicated randomized trial with infection as the primary outcome has not been conducted, so the current evidence, while consistent, is best described as strongly suggestive rather than definitive.

Key Takeaways

The weight of current evidence points in a reassuring direction: GLP-1 medications are associated with fewer serious infections, not more. Across 164,000 trial participants, serious infections fell by roughly 11%, respiratory illness by 14%, and severe COVID-19 by 18% — with a mortality signal in the SELECT trial driven partly by fewer infectious deaths.

Three practical points follow for patients:

The benefit appears to be about severity, not exposure. These drugs seem to reduce how badly an infection hits, likely by calming an overactive immune response, rather than preventing you from catching something.
Metabolic improvement is part of the mechanism. Better blood sugar and meaningful weight loss restore immune defenses that obesity and diabetes erode, which is one reason adherence matters.
Procedural caution is still warranted. Reduced infection risk does not cancel the separate, motility-based aspiration concern around surgery — always tell your care team you are on a GLP-1 drug.

No one should start a GLP-1 medication to prevent infection; that is not an approved use, and the definitive randomized evidence does not yet exist. But for the millions already taking these drugs for weight and metabolic health, the data offer a genuine reassurance: the immune trade-off many feared has not materialized, and the balance so far tilts toward protection.

References

Han S, et al. Association of glucagon-like peptide-1 receptor agonist use with risk of infections: a systematic review and meta-analysis. Journal of Infection. 2025. DOI: 10.1016/j.jinf.2025.106645
Yu M, et al. The relationship between the use of GLP-1 receptor agonists and the incidence of respiratory illness: a meta-analysis of randomized controlled trials. Diabetology & Metabolic Syndrome. 2023;15:164. DOI: 10.1186/s13098-023-01118-6
Scirica BM, et al. The effect of semaglutide on mortality and COVID-19–related deaths: an analysis from the SELECT trial. Journal of the American College of Cardiology. 2024. DOI: 10.1016/j.jacc.2024.08.007
Kazi MAI, et al. Glucagon-like peptide-1 receptor agonist therapy and risk of pulmonary and systemic infections in diabetic gastroparesis: a propensity-matched cohort study. Advances in Respiratory Medicine. 2026;94(2):20. DOI: 10.3390/arm94020020
Alharbi SH. Anti-inflammatory role of glucagon-like peptide 1 receptor agonists and its clinical implications. Therapeutic Advances in Endocrinology and Metabolism. 2024;15. DOI: 10.1177/20420188231222367

Last updated: 2026-07-14 Medical review: Dr. James Chen, MD, PhD, FACE