Provided herein are methods for modulating the intestinal microbial profile and for reducing intestinal dysbiosis in type 2 diabetic or pre-diabetic subjects, comprising administering metformin or a derivative or salt thereof and one or more probiotic microorganisms selected from Lactobacillus plantarum, Lactobacillus bulgaricus, Lactobacillus gasseri, Bifidobacterum breve, Bifidobacterium animalis subsp. lactis, Bifidobacterium bifidum, Streptococcus thermophilus and Saccharomyces boulardii. Also provided are methods for treating type 2 diabetes or an associated metabolic complication or condition and for delaying the onset of type 2 diabetes in pre-diabetic subjects, comprising administering one or more probiotic microorganisms selected from Lactobacillus plantarum, Lactobacillus bulgaricus, Lactobacillus gasseri, Bifidobacterum breve, Bifidobacterium animalis sub sp. lactis, Bifidobacterium bifidum, Streptococcus thermophilus and Saccharomyces boulardii.