Diabetes Medication May Impair Exercise Benefits, Study Finds

A common diabetes medication may diminish exercise benefits, according to new research that challenges conventional thinking about combining these treatments.

Researchers from Rutgers University have discovered that metformin, one of the most widely prescribed medications for type 2 diabetes, could reduce some of the key health improvements typically gained through regular exercise.

The study, published in The Journal of Clinical Endocrinology & Metabolism, found that adults who took metformin while following an exercise regimen experienced smaller improvements in blood sugar control, vascular function and aerobic fitness compared to those who exercised without the medication.

“Metformin is the most widely used glucose-lowering medication used around the world,” explained Steven Malin, lead study author and professor in the Department of Kinesiology and Health at Rutgers’ School of Arts and Sciences. “However, it is not clear that taking both of these treatments together is best.”

The findings have significant implications for the approximately 35 million Americans with type 2 diabetes and millions more worldwide who take metformin for blood sugar management or experimental anti-aging purposes.

The 16-week, double-blind clinical trial involved 72 adults at risk for metabolic syndrome—a cluster of conditions including high blood pressure, elevated blood sugar, and excess abdominal fat that increase risk for diabetes and cardiovascular disease. Participants were divided into four groups: two performed either high- or low-intensity exercise while taking a placebo, while the other two followed the same exercise protocols but received 2,000 milligrams of metformin daily.

By the study’s conclusion, participants who exercised without metformin demonstrated marked improvements in vascular insulin sensitivity, meaning their blood vessels responded better to insulin and allowed increased oxygen and nutrient delivery to muscles. However, these gains were significantly reduced in the groups taking metformin. The medication also appeared to diminish exercise-related reductions in inflammation and fasting glucose levels.

While researchers haven’t definitively identified the mechanism behind this interaction, they believe metformin may interfere with the body’s cellular adaptations to exercise.

“Improved blood vessel function is key for delivering nutrients to tissues, like sugar,” Malin explained. “If the sugar cannot be delivered to the tissue, this might explain why muscles cannot use the sugar for energy as well in response to insulin.”

The researchers emphasized that the study’s relatively small sample size and focus on people at risk for metabolic syndrome—rather than those already diagnosed with diabetes—means the findings may not apply universally. They stressed that patients should not discontinue medication or exercise regimens without consulting healthcare providers.

Medical experts not involved in the research have urged caution in interpreting the results. Dr. David Cutler, a board-certified family medicine physician at Providence Saint John’s Health Center in California, noted that the modest decrease in vascular insulin sensitivity needs to be weighed against metformin’s substantial benefits.

“The small decline in vascular insulin sensitivity needs to be weighed against the great benefit from lowered blood sugar levels achieved with metformin,” Cutler said. “The lowering of blood sugar results in lower risks of all diabetic complications like heart attack, stroke, kidney failure, blindness and amputation.”

The findings may have more relevance for individuals using metformin for purposes other than diabetes management, such as anti-aging, polycystic ovary syndrome, or cancer prevention—areas where the drug is increasingly being prescribed.

“For now, metformin should remain the first-line medication for treating type 2 diabetes,” Cutler added.

The Rutgers research team is now investigating whether metformin interacts differently with resistance or strength training, and if adjusting dosage or timing could minimize the interference with exercise benefits. This work represents an important step in optimizing treatment approaches for the growing population of patients with diabetes and prediabetic conditions.

As diabetes rates continue to climb globally, understanding how common treatments interact will be crucial for developing more personalized and effective treatment plans that maximize health benefits while minimizing unwanted effects.