Ketone Pharmacokinetic Study in HFrEF

Inclusion Criteria: * Diagnosis of HFrEF (ejection fraction\<=45%) * Systolic blood pressure greater \>=90 mmHg Exclusion Criteria: * Intentional ketogenic (high fat, low carbohydrate) diet (must be off ketogenic diet for \>7 days prior to visit) * Significant liver disease (cirrhosis) or alcohol abuse disorder (\>14 drinks/week). * Unique cardiomyopathies: infiltrative/hypertrophic cardiomyopathy, pericardial disease, or other cardiomyopathies that in the investigator's opinion have unique treatment options that would be less likely to be affected by ketone therapy. * Estimated glomerular filtration rate\<25 mL/min/1.73 m2 as the most recent value in the last year. * Type 1 diabetes mellitus * Use of ventricular assist device, history of heart transplant, or use of continuous inotropes * Pregnant women. Due to unknown affects of nutritional ketosis in pregnant women, pregnancy will be an exclusion. Accordingly, women of childbearing age with a menstrual cycle within the past year will be asked to submit a urine specimen for pregnancy testing.