Type 2 diabetes mellitus (T2DM) accounts for most diabetes worldwide and is among the fastest-growing chronic conditions in adults. This narrative review synthesises recent evidence (mainly 2023–2026) on the prevalence and clinical profile of T2DM in adult populations, drawing on global surveillance and burden estimates, a national Indian survey, systematic reviews of complications, and a meta-analysis of prevention trials. Estimates of adults living with diabetes range from roughly 590 to 830 million, depending on age range and method, and T2DM represents about 96% of cases in global burden analyses. Prevalence rises steeply with age, is higher in urban settings, and is concentrated in low- and middle-income countries, where many cases remain undiagnosed or untreated. Excess adiposity is the leading modifiable driver, although South Asian adults often develop T2DM earlier and at lower body mass index. Roughly one in four adults with T2DM has chronic kidney disease, and about one in three has cardiovascular disease. Lifestyle programmes producing modest weight loss reduce progression from prediabetes, yet cost, workforce shortages, and delayed diagnosis limit control. The evidence supports earlier risk-based detection, screening that does not rely on body mass index alone, and stronger primary-care pathways.