 Subject is not on active military duty; Subject is not currently participating in another clinical trial; Subjects current GFR is not 50 ccmin1.73m2; Subject does not have diabetes; Subject does not have a systemic disease other than hypertension and PKD; Subject does not have a solitary kidney; Subject does not have an allergy or intolerance to metformin; Subject is not pregnant or lactating or intending to become pregnant within the next three years; Subject does not have an unstable or unclipped cerebral aneurysm; Subject does not have active coronary artery disease; Subject does not have an MRI incompatible deviceimplant; Subject does not have severe claustrophobia; Subject has not had any solid organ transplant; Subject does not have a Vitamin B12 deficiency; Subject does not currently take any medications that interact with metformin, such as nifedipine, furosemide, cationic drugs amiloride, ranitidine, triamterene digoxin, procainamide, quinidine, vancomycin, trimethoprim; 