Metabolic acidosis is associated with vascular endothelial dysfunction and is a common complication in patients who have received a kidney transplant. Kidney transplant recipients (KTR) with lower serum bicarbonate levels, even within the normal range, have an increased risk of graft loss and mortality. The investigators propose a prospective, double-blind, randomized, placebo-controlled, 18-week crossover pilot study to examine the effects of sodium bicarbonate on vascular endothelial function, graft function, and cognitive function in 20 KTR patients.

Inclusion Criteria:

• Age ≥ 18 years
• Kidney transplant received at least 1 year ago
• Serum bicarbonate 20-26 mEq/L on 2 separate measurements (at least 1 day apart)
• eGFR >45 ml/min/1.73m2
• Blood pressure <140/90 mm Hg prior to randomization
• BMI < 40 kg/m2 (FMD measurements can be inaccurate in severely obese patients).
• Able to provide consent
• Stable kidney transplant medication regimen for at least 1 month prior to randomization
• Stable anti-hypertensive regimen for at least one month prior to randomization
• Not taking medications that interact with agents administered during experimental sessions (e.g. sildenafil interacts with nitroglycerin).

Exclusion Criteria:

• Significant comorbid conditions that lead the investigator to conclude that life expectancy is less than 1 year
• Use of chronic daily oral alkali within the last 3 months (including sodium bicarbonate, calcium carbonate or baking soda)
• Uncontrolled hypertension
• Serum potassium < 3.3 or ≥ 5.5 mEq/L at screening
• New York Heart Association Class 3 or 4 heart failure symptoms, known EF ≤30%, or hospital admission for heart failure within the past 3 months · Factors judged to limit adherence to interventions
• Current participation in another research study
• Pregnancy or planning to become pregnant or currently breastfeeding
• Chronic use of supplemental oxygen