The objective of our study is to evaluate and understand the dose relationship between metformin, inflammation, thrombosis, and the microbiome, while correlating changes in cellular respiration with changes in physiologic parameters in non diabetic, pre-frail adults. We plan to gather stool samples, blood samples, and baseline physiologic parameters on all patients. Patients will then be exposed to 90 days of metforminER (at either 500mg, 1000mg, or 1500mg) or placebo. The same samples will be gathered again at 30, 60, and 90 days. At 90 days, we may retest physiologic parameters. At 120 days, we will retest physiologic and laboratory parameters in order to evaluate changes over time.