Improve PAD PERformance With METformin

Inclusion Criteria: All participants will have PAD. PAD will be defined as follows: * First, an ankle brachial index (ABI) \<=0.90 at the baseline study visit is an inclusion criterion for PAD. * Second, potential participants who have an ABI \> 0.90 but ≤ 1.00 and experience a 20% or higher drop in ABI after heel-rise exercise will be eligible. * Third, potential participants with an ABI \> 0.90 who have vascular lab evidence of PAD or angiographic evidence of PAD who have ischemic symptoms during the six-minute walk and/or treadmill exercise stress test will be eligible. * Fourth, potential participants with a history of lower extremity revascularization who do not meet the criterion above and have an ABI \> 0.90 with a 20% or higher drop in ABI after heel-rise exercise will be eligible. Exclusion Criteria: * Above- or below-knee amputation. * Critical limb ischemia. * Wheelchair-bound or requiring a walker to ambulate. * Walking is limited by a symptom other than PAD. * Current foot ulcer on bottom of foot. * Diabetes mellitus defined as one or more of a) patient report of physician diagnosed diabetes mellitus, b) use of one or more diabetes medications, c) two baseline hemoglobinA1C values of \>6.5, d) two fasting glucose values \>126 mg/dl. \[NOTE: the second fasting glucose value and hemoglobin A1C values will be at the discretion of the principal investigator. For example, if the first glucose value is \>300 or the first A1C value is \>6.9, then investigators may d…