The Impact of High‐Dose Vitamin D on Hemoglobin Concentrations in Critical Illness

Objective Anemia and vitamin D deficiency are highly prevalent in critically ill patients, and vitamin D may be involved in the regulation of iron recycling. The purpose of this study was to examine the impact of vitamin D therapy on hemoglobin concentrations in critically ill patients. Methods We conducted a secondary analysis of a randomized, double‐blinded, placebo‐controlled trial of high‐dose vitamin D 3 (D 3 ) therapy in critically ill adults requiring mechanical ventilation (N=30). Participants were randomized to receive a total enteral dose of 500,000 IU D 3 , 250,000 IU D 3 , or placebo administered over 5 days. Blood was drawn weekly throughout hospitalization for up to 4 weeks. Linear mixed effects models were used to assess change in hemoglobin concentration by treatment group over time. Results The prevalence of anemia at baseline was 93.3%. Baseline mean hemoglobin and plasma 25‐hydroxyvitamin D concentrations were 9.7 g/dL (SD=1.9) and 21.4 ng/mL (SD=9.1), respectively, and did not differ significantly across treatment groups. In the 250,000 IU D 3 group, change in hemoglobin over time did not differ from placebo ( P =0.5). However, in the group who received 500,000 IU D 3 , hemoglobin concentrations increased by 0.8 g/dL (SE=0.3) per week ( P =0.005). Conclusion In this population of critically ill patients, treatment with 500,000 IU D 3 over 5 days increased hemoglobin concentrations during hospitalization, while no significant change in hemoglobin was observed in the 250,000 IU D 3 or placebo groups. These findings support a role for vitamin D in improving hemoglobin concentrations in critical illness, which should be confirmed in larger studies. Funding: T32 DK7734‐17, R21 HL110044