['To assess the impact of vitamin D supplementation (cholecalciferol) on the insulin sensitivity and metabolic health of patients with chronic kidney disease (CKD).', 'Twenty-eight adult patients with CKD stages 3-4 were recruited from the outpatient department of the Princess Alexandra Hospital (Brisbane, Australia) to a double-blind randomized trial of cholecalciferol (vitamin D3) 2000\u2009IU/day or placebo for 6 months. Metabolic parameters at baseline were compared with 20 non-CKD adults. The primary outcome was an improvement in insulin resistance (glucose disposal rate, GDR) at 6 months (quantified by hyperinsulinaemic euglycaemic clamp). Carbohydrate and lipid oxidation rates were assessed by indirect calorimetry.', 'At baseline, patients were significantly insulin-resistant compared with lean younger non-CKD individuals (n\u2009=\u20099; GDR 3.42 vs. 5.76\u2009mg/kg per minute, P\u2009=\u20090.001), but comparable with their age-, gender- and weight-matched non-CKD counterparts (n\u2009=\u200911; 3.42 vs. 3.98\u2009mg/kg per minute, P\u2009=\u20090.4). 25-Hydroxyvitamin D did not change in the placebo group, but rose from 95\u2009±\u200937 to 146\u2009±\u200925\u2009nmol/L with treatment (P\u2009=\u20090.0001). Post treatment, there was no difference in GDR between groups (GDR 3.38 vs. 3.52\u2009mg/kg per minute, ancova P\u2009=\u20090.4). There was a relative increase in hyperinsulinaemic oxidative disposal of glucose with treatment (within-group P\u2009=\u20090.03).'] Does vitamin D improve the metabolic health of patients with chronic kidney disease stage 3-4 : a randomized controlled trial?