Researchers at Stanford University have identified a possible survival benefit for people with type‑2 diabetes who were taking the common medication metformin when they contracted COVID‑19. An analysis of more than 53,000 U.S. medical records, published in the journal Diabetes, Obesity and Metabolism, showed that metformin users were 39 % less likely to die within a year of infection compared with patients using a different class of diabetes drug.
Study design and key findings
The retrospective cohort included 53,332 adults aged 30 to 85 who tested positive for COVID‑19 between October 2021 and November 2023. All participants had a prior diagnosis of type‑2 diabetes and had been prescribed either metformin or a dipeptidyl peptidase‑4 inhibitor (DPP‑4i) at least one month before their COVID‑19 diagnosis.
Among the cohort, 50,965 patients (96 %) were on metformin, while 2,367 (4 %) were taking a DPP‑4i. The metformin group was slightly younger on average—60 years versus 64 years for the DPP‑4i group. After adjusting for age, gender and other recorded variables, researchers found that metformin use was associated with a significantly higher probability of surviving the subsequent twelve months.
The initial analysis also hinted at a 13 % reduction in long‑COVID symptoms among metformin users, but further statistical testing did not confirm this as a significant association.
Possible biological mechanisms
Metformin’s primary function is to lower blood glucose and improve insulin sensitivity, which can bolster immune defenses weakened by high blood sugar, according to the CDC. The study authors noted that the drug may also influence a biological pathway that regulates blood pressure and fluid balance—factors known to affect COVID‑19 severity. Earlier investigations have suggested metformin can dampen inflammation and reduce viral load during active infection.
These mechanisms align with a separate study from the University of Minnesota Medical School that reported patients who began metformin within six days of a COVID‑19 diagnosis were less likely to die or develop long‑COVID. However, both studies emphasize that observational findings do not establish causality.
Expert commentary and study limitations
Ziyad Al‑Aly, M.D., a senior clinical epidemiologist at Washington University in St. Louis, told Fox News Digital that metformin is typically the first medication prescribed for type‑2 diabetes, while DPP‑4 inhibitors are often used later or for patients who cannot tolerate metformin due to age, kidney disease, or other health issues. “Put simply, people on metformin are generally healthier than people on DPP‑4 inhibitors,” Al‑Aly said.
Al‑Aly cautioned that the study’s reliance on existing medical records, rather than a randomized trial, means the observed survival advantage cannot be definitively attributed to metformin. He highlighted that patients on DPP‑4i were older and carried more comorbidities, which could have contributed to their higher mortality risk. Additionally, the researchers did not have complete data on patients’ COVID‑19 vaccination status.
“This is not enough evidence to change treatment,” Al‑Aly added. “People take a DPP‑4 inhibitor because they need it to control their diabetes, usually because metformin was not enough or was not an option for them.” He warned against switching medications based solely on these findings and called for large, well‑designed randomized trials to confirm any protective effect.
While the Stanford analysis adds to a growing body of literature suggesting metformin may have benefits beyond glucose control, clinicians and patients are advised to continue current diabetes management plans until more definitive evidence emerges.
Mitchell Landsberg is a Senior Technology Correspondent at News Raise. He covers consumer electronics, artificial intelligence, software developments, and digital privacy trends.
