The Role of Vitamin D in the Pathophysiology of Chronic Failure

The inclusion criteria for the study is: * an EF ≤40% within the last 12 months before recruitment * established diagnosis of heart failure * \>18 years of age * patients will vitamin d levels of sufficient, mild deficiency and severe deficiency The exclusion criteria is: * hypercalcemia * known hypersensitivity to Vitamin D * patient unwilling to comply with study requirements * any other disease other than heart failure that can alter the patients quality of life over a period of 6 months * women of child bearing potential * a patient currently taking vitamin d * severe renal impairment estimated glomerular filtration rate (eGFR) \<30