AIM Diabetes and vitamin D deficiency are widely prevalent in India. Studies have proven correlation between low vitamin D levels and pulmonary tuberculosis (PTB) and low vitamin D levels and insulin resistance. We evaluated the effects of vitamin D supplementation on type 2 diabetes mellitus patients with pulmonary tuberculosis (PTB). METHODS Forty-five subjects (M:F=34:11) were screened. Inclusion criteria were age >15 years, newly diagnosed PTB cases with uncontrolled diabetes, serum vitamin D<20 ng/ml. The patients with vitamin D level<20 ng/ml were randomly assigned to 2 groups. Group 1 subjects received oral cholecalceferol (60,000 units/week) and calcium carbonate (1g/day) along with anti tubercular treatment (ATT), while group 2 subjects did not. Sputum was checked at interval of 2 weeks for 12 weeks. Primary end point was time to achieve sputum smear conversion. RESULTS Fifteen patients having vitamin D>20 ng/ml were excluded. Age of the patients was 42.9±13.2 years and serum vitamin D levels were 18.4±15.3 ng/ml. Sputum smear conversion was 6 weeks in group 1 versus 8 weeks in group 2 (p=0.067). Glycated hemoglobin levels reduced from 11.1±1.3 to 7.7±0.9 in group 1 versus 10.3±1.2 to 7.8±1.1 (p>0.1). CONCLUSION Vitamin D can serve as adjuvant treatment of tuberculosis in diabetics with vitamin D deficiency. Further studies are required to validate this observation and define a cut off for vitamin D level to prevent immunological alterations.