Inclusion Criteria:

• * Have documented heart failure as a treated inpatient or outpatient diagnosis in the medical record.
• * Left ventricular ejection 40% within the past 12 months either by echocardiogram, cardiac MRI, cardiac CT, nuclear imaging or cardiac catheterization.
• NYHA class II-III
• * On stable GDMT for at least 2 weeks (including at least an EBM dose of betablocker and RAAS inhibition) consistent with the EPHESUS trial criteria \[16\] or having a documented allergy or adverse reaction to betablocker and/or RAAS inhibition.
• * Age 18 years or older.

Exclusion Criteria:

• * Acute coronary syndrome or cardiac revascularization within the past 3 months.
• * End stage renal disease with renal replacement therapy or creatinine clearance less than 30 ml/min \[17\].
• * Cardiac resynchronization therapy within the past 3 months.
• * Constrictive pericarditis or restrictive cardiomyopathy on cardiac imaging study (echocardiogram cardiac MRI, cardiac CT) within the last 12 months.
• * Ablation for cardiac arrhythmias within the past month.
• * Peripartum cardiomyopathy diagnosed within past 6 months. If LVEF is still 40% after 6 months of diagnosis, they can be enrolled into the study.
• * Uncorrected cyanotic congenital heart disease.
• * Severe right sided valvular disease and/or greater than moderate degree of stenotic or regurgitant left valvular disease.
• * Terminal illness with expected survival of less than 12 months.
• * Women who are pregnant, breast feeding, or plan to become pregnant during the study. All women in childbearing age will undergo baseline and quarterly urine pregnancy tests to ensure absence of pregnancy since the cardiometabolic assessments will be different during pregnancy.
• * Oral therapy with probenecid for any indication during the preceding 3 months.
• * Hypersensitivity to probenecid based on prior exposure.
• * Inability to provide informed consent or study procedures due to dementia, unstable psychiatric disease, or other cause (e.g. inability to do perform exercise testing).
• * Acute gout attack within the previous 3 months.
• * History of uric acid kidney stones within the last year. Patient will be removed from the study if they develop urate kidney stones.
• * History of blood diseases in the past year: Aplastic anemia, Hemolytic anemia, Leukopenia, Neutropenia, Pancytopenia, Thrombocytopenia or leukemia.
• * Creatinine clearance (eGFR) \<30 ml/min.