OBJECTIVES: To assess the benefits and harms of vitamin B and/or its derivatives in patients with diabetic kidney disease (DKD). METHODS: We searched the Cochrane Renal Group's Specialized Register CENTRAL; MEDLINE OVID SP; Hand searching of renal journals and conference proceedings; EMBASE OVID SP; the International Clinical Trials Register (ICTRP) Search Portal & ClinicalTrials.gov. Randomized controlled trials (RCTs) comparing vitamin B and/or its derivatives with placebo, no or active treatment, in patients with DKD were included. RESULTS: Out of 56 identified studies, four studies were found to be suitable for inclusion. A total of 745 participants were randomized to either vitamin B derivatives (benfotiamine (300 mg TID), thiamine (300 mg OD), vitamin B12 (500 mg OD), folic acid (2.5 mg OD), vitamin B6 (25 mg OD)) or placebo or active control.  Treatment duration ranged from 3 months to 36 months. We found that none of those derivatives improved kidney function: improved creatinine clearance (Mean difference (MD) 2.00, 95% CI -21.78 to 25.78, P = 0.87), decreased serum creatinine level (MD 1.00 , 95% CI -7.88 to 9.88, P = 0.83), reduce level of urinary albumin excretion  level (MD: -16.75, 95% CI -103.44 to 69.94, P = 0.70), improved the glomerular filtration rate (MD: -7.00, 95% CI -22.33 to 8.33, P = 0.37) significantly compared to placebo or active control. In addition, we found that risk of myocardial infarction, stroke, revascularization, and all-cause mortality, in the B-vitamin combination therapy group was increased (Risk Ratio 1.85, 95% CI 0.99 to 3.45, P= 0.05). We also found no significant difference between vitamin B combination therapy and control group for serious adverse events, and one or more adverse events. CONCLUSIONS: We did not find any improvement in kidney function, following use of vitamin B preparation. These findings require confirmation from high quality randomized trials.