Metformin, a widely prescribed drug for type 2 diabetes, could offer a powerful new tool in the fight against long Covid. Recent research suggests that when given early in the course of a Covid-19 infection, metformin may reduce the risk of developing long Covid by 40% to 50%, with some studies showing an even greater benefit.
Primarily used to improve insulin sensitivity, metformin also influences immune response and cellular metabolism, lending it antiviral properties that have intrigued scientists since the start of the pandemic. Its affordability and widespread availability make it an attractive candidate for repurposing in Covid treatment.
Long Covid, first identified in 2020, describes persistent symptoms such as fatigue, breathlessness, chest pain, and cognitive difficulties—often called brain fog—that linger for months or years after the initial infection. These symptoms can severely impact quality of life and the ability to work.
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To explore metformin’s potential, researchers analyzed data from randomized clinical trials and real-world studies published in the Clinical Infectious Diseases journal. A landmark study, the COVID-OUT trial initiated in 2021, demonstrated that metformin decreased the incidence of long Covid by 41% over a 10-month period. Notably, patients who began treatment within three days of symptom onset experienced a 63% reduction in long Covid risk, underscoring the importance of early intervention.
The trial also observed that metformin lowered the viral load—the quantity of virus present in bodily fluids—potentially limiting disease severity. However, this study was limited to participants with a body mass index (BMI) of 25 or higher and excluded individuals with previous Covid-19 infections.
To validate these findings, the ACTIV-6 trial tested the same 500mg dosage on a broader population. It found a 50% reduction in clinical diagnoses of long Covid among metformin users, supporting the earlier results but stopping short of definitive confirmation.
Both studies administered 36 doses over approximately two weeks, gradually increasing the dosage without causing significant side effects such as digestive distress.
These findings highlight metformin’s promise as a safe, accessible intervention that could drastically reduce the long-term impact of Covid-19—provided it is started promptly after infection.