A convenience sample of 40 subjects (20 per treatment group) will be prospectively recruited from the Royal Columbian Hospital (RCH) Heart Function (HFx) Clinic. Subjects will be randomized to receive either vitamin D3 (cholecalciferol) or a matching placebo at a dose of 20,000 IU daily for 30 days followed by 20,000 IU once weekly for 8 weeks. Subjects will have their 25OHD levels measured, self-administer the EQ-5D™ and BPI questionnaires and perform the 6MWT at the study entry and again at the completion of the study (12 weeks after entry).