Diabetic kidney disease (nephropathy) develops in nearly 40% of patients with type 2 diabetes mellitus. Diabetic nephropathy is caused by damage to the small blood vessels in the kidneys due to uncontrolled blood sugar levels, which mean that the kidneys become less effective at filtering urine. This is associated with albuminuria (protein in the urine). Treatment with some drugs reduces the loss of albumin through the urine and delays disease progression. There is increasing evidence that vitamin D could also be important in management of diabetic kidney disease. The aim of this study is to investigate the efficacy and safety of a combined regimen of calcitriol (active vitamin D) and established drugs for diabetic kidney disease.