A meta-analysis of 19 studies found that taking metformin, a common diabetes drug, may raise lactate concentrations during exercise. Lactate is a natural byproduct of physical activity, but higher levels can sometimes cause muscle fatigue or discomfort.
The analysis included 325 adults with prediabetes or type 2 diabetes, as well as some healthy young males in acute studies. Participants took metformin either as a single dose or over time. The researchers compared exercise metabolism and capacity, focusing on lactate, glucose, insulin, and free fatty acids.
Results showed that metformin was linked to greater lactate levels during exercise, with a moderate to large effect size. However, the study did not report on safety issues like side effects or how well people tolerated the drug. The authors note that the effects may vary based on dose, duration, and individual characteristics.
This review provides useful insights for clinicians and exercise professionals. But because it is a meta-analysis of existing studies, it cannot prove cause and effect. People taking metformin should talk to their doctor before changing their exercise routine.