The goal of this pilot, randomized, single-blind, placebo-controlled trial is to evaluate the feasibility of and provide preliminary information for a multi-center randomized controlled trial that will assess the effects of metformin on blood sugar control in patients after total hip or total knee replacement surgery.

The primary objective of this study is to assess the feasibility of conducting a large, randomized trial with regards to timely recruitment, study drug administration, protocol adherence, and overall retention in patients undergoing total joint arthroplasty.

Secondarily, the investigators aim to obtain preliminary estimates of group-specific outcome means and variances for primary and secondary outcomes of a larger future trial.

Inclusion Criteria:

• Male or female, age 18-99 years
• Undergoing total hip or total knee arthroplasty, including elective, primary, and revision surgeries
• Ability to take oral medication and be willing to adhere to the prescribed metformin regimen regardless of current, past, or no metformin use.

Note: Patients with or without type 2 diabetes are considered eligible. (E.g.)

• Type 2 diabetic on metformin
• Type 2 diabetic on metformin and other medication, including insulin
• Type 2 diabetic on medication but not metformin
• Pre-diabetic
• Non-diabetic

Exclusion Criteria:

• Advanced renal insufficiency (glomerular filtration rate (GFR) < 45, or chronic kidney disease (CKD) stage 3B or higher)
• Advanced liver cirrhosis or failure (Child-Pugh class B or C)
• Congestive heart failure (New York Heart Association (NYHA) class 3 or 4)
• Current alcohol abuse within 30 days of surgery (>4 standard servings daily for men, >3 standard servings daily for women)
• Type 1 diabetes
• Received contrast dye within 48 hours of surgery
• Vulnerable populations: Children, pregnant women, neonates, decisionally impaired adults, prisoners