Subgroup analysis. Subgroup analysis. Effect of vitamin D supplementation on outcome variables in subgroups defined by baseline levels of the respective outcome variables. Effect estimates for each outcome variable are difference in change from baseline to 16 weeks between the combined intervention groups (10 or 25 µg) and the placebo group. Within each subgroup, the effect estimate was adjusted for the baseline level of the respective outcome variables (baseline value entered as a continuous variable in the regression model). Ahmed A Madar et al. BMJ Open Diab Res Care 2014;2:e000026 ©2014 by American Diabetes Association