- Metformin may blunt blood vessel improvements gained from exercise.
- Effects were strongest during high-intensity workouts in older adults.
- Experts recommend speaking to a doctor before changing medication routines.
A new study suggests metformin, one of the most widely used diabetes medications, may dampen some of the blood vessel benefits people typically get from exercise.
Researchers from Rutgers University found that adults at risk for metabolic syndrome who exercised while taking metformin didn’t see the same improvements in vascular insulin sensitivity as those who exercised without the medication.
Exercise helps blood vessels respond better to insulin, improving blood flow to muscles. Metformin also has vascular effects of its own and can improve blood flow in some conditions. But very few studies have tested how the two interact, which is what this new trial set out to examine.
How Was the Study Conducted?
For this study, researchers sought out participants in Virginia and New Jersey, then conducted physical examinations on each potential participant to determine their eligibility. None of the participants could be using medication known to affect insulin levels, though the researchers did make an exception for hypertension medication.
The study included middle aged and older men and women, mostly in their 50s, who were sedentary and at risk for metabolic syndrome. Participants were randomly assigned to 16 weeks of low- or high-intensity treadmill exercises and given either metformin or a placebo.
Before and after the program, the study team tested how well insulin could widen both large arteries and tiny capillaries in the arm—a way to measure vascular insulin sensitivity. Before these tests, all participants were provided with 24 hours of meals that aligned with nutrition parameters from the American Heart Association.
What Did the Study Find?
People who exercised without metformin showed clear improvements in how their blood vessels responded to insulin. Those gains were strongest in the high-intensity exercise group that took the placebo.
In contrast, participants who exercised while taking metformin saw smaller improvements. The blunting effect was most noticeable during high-intensity exercise, where metformin users had far less of an increase in vessel responsiveness than those taking a placebo. Metformin users also saw less improvement in some metabolic markers, including fasting glucose.
How Does This Apply to Real Life?
Exercise is still one of the most effective tools for improving metabolic and cardiovascular health, and metformin is a trusted treatment for type 2 diabetes and insulin resistance. This study doesn’t suggest people should stop taking metformin.
Instead, the findings show a need for more research on how medications and lifestyle habits interact—especially when they are prescribed together. If you’re taking metformin and want to learn more about how it may interact with your exercise routine or diet, speak to a trusted healthcare professional. They can help you understand how these findings may apply to you and offer personalized advice to help manage your insulin levels.
Our Expert Take
This study offers an early look at how metformin may influence the way blood vessels adapt to exercise. The results are intriguing but come from a small sample, so larger trials are needed. If you take metformin and have an active exercise routine, consider talking with a healthcare provider about the best way to combine both in your overall treatment plan.
