Abstract Introduction The cause-effect relationships of dysbiosis and type 2 diabetes are complex and remain to be elucidated, very likely a two-way interaction. The aim of the study was to evaluate intestinal microbiota composition in patients with type 2 diabetes. Material and Methods This is a case-control study among patients with type 2 diabetes. Individuals were eligible if they were aged ≥18 years, were newly diagnosed with type 2 diabetes, had HbA1c levels ≥6.5 and ≤10.0%, and have been treated for oral antidiabetic agents for 3 months. The primary endpoint was the change from baseline in intestinal microbiota compositon after 12 weeks of treatment and comparison with healthy controls. Secondary endpoints were; change from baseline in intestinal microbiota composition after 12 weeks of oral antidiabetic monotherapy and comparison with healthy controls. A minimum of 5 mL fresh stool sample was collected at Day O of the study and 12 weeks later in a 15 mL Falcon tube and rapidly transferred to −80 °C to be stored in an upright position until DNA extraction. The V3 and V4 regions of the 16S rRNA gene were amplified following the 16S Metagenomic Sequencing Library Preparation. RESULTS: During the study period, 44 eligible patients were planned to enroll the study. Detailed analysis has been performed in 24 patients with type 2 diabetes (receiving oral antidiabetic treatment, metformin or linagliptin) and 10 age-matched healthy controls. The Chao-1 and Shannon Index were lower in the type 2 diabetes group before and after treatment groups (p<0.01 for both). PCoA plots were constructed to demonstrate separation of groups of samples for unweighted UniFrac distance, weighted UniFrac distance, and Bray–Curtis dissimilarity distance and no statistically significant differences between or within the type 2 diabetes and healthy control groups. At the first visit (before treatment), at phylum level, Bacteroidetes abundance have been observed in diabetic group, while Actinobacteria and Firmicutes in healthy controls. At genera level, we observed Gemmiger and Collinsella predominance in diabetes group; however, Faecalibacterium, Bacteroides and Alistipes in healthy controls. After 12 weeks of treatment, at genera level, Lactobacillus, Rothia and Collinsella increased in type 2 diabetes group however, microbiota composition was still different comparing the healthy controls. In patients receiving 12 weeks of metformin, Prevotella and Lactobacillus increased at genera level while Dialister and Ruminocococcus decreased. DISCUSSION: We report that there is a substantial change in the composition of the gut microbiota in patients with type 2 diabetes. We observed the beneficial effects as relative abundance of short chain fatty acid producing bacteria increased (eg, Prevotella, Lactobacillus) in metformin group. The interaction of the anti-diabetic drugs with gut microbiota have been less studied, further studies will highlight the clinical effect of these alteration in intestinal microbiota composition in diabetes. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Monday, June 13, 2022 12:37 p.m. - 12:42 p.m.