Both, anemia and vitamin D deficiency are prevalent in patients with heart failure. According to recent evidence, vitamin D may stimulate erythropoiesis. We measured circulating 25-hydroxyvitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25[OH]₂D) and hemoglobin (Hb) in a cross-sectional study in 364 end-stage heart failure patients awaiting cardiac transplantation, of whom 52.6% met the criteria for anemia (Hb < 13 g/dl in males and <12 g/dl in females). None of the patients were on erythrocyte-stimulating agents. Of the study cohort, 87.8% had 25(OH)D concentrations below 50 nmol/l. The mean Hb concentrations were significantly reduced in the lower tertiles of 25(OH)D and 1,25(OH)₂D (P < 0.001). In multivariate-adjusted logistic regression analyses, the odds ratios for anemia of the lowest tertile of 25(OH)D (<18 nmol/l) and 1,25(OH)₂D (<40 pmol/l) were 2.69 (1.46–5.00) and 4.08 (2.18–7.62) compared with their respective highest tertile (>32 nmol/l and >70 pmol/l). Patients with severe dual deficiency of 25(OH)D and 1,25(OH)₂D had an odds ratio for anemia of 9.87 (95% CI 3.59–27.1) compared with patients in the highest tertile for both vitamin D metabolites. Circulating 1,25(OH)₂D was directly related to circulating 25(OH)D levels and kidney function (P < 0.001), and inversely associated with C-reactive protein (P = 0.020).

Our data demonstrate that vitamin D deficiency is independently associated with low Hb values and anemia in end-stage heart failure. Circulating 1,25(OH)₂D is a better predictor of anemia than circulating 25(OH)D. Prospective randomized studies with administration of vitamin D (metabolites) will have to clarify if the association of vitamin D deficiency with anemia is causal.