Glycosylation is a vital post-translational modification crucial for protein function, folding, and stability. Disorders of protein glycosylation have significant implications for human diseases, including diabetes mellitus. This review explores the biological mechanisms underpinning protein glycosylation, types of glycosylation disorders, and their clinical manifestations, focusing on their association with diabetes. Recent studies demonstrate shared molecular pathways between glycosylation disorders and diabetes pathophysiology, emphasizing oxidative stress, inflammation, and impaired insulin signaling. Understanding these links offers prospects for novel diagnostic strategies and therapeutic interventions. Continuous research into the molecular crosstalk between glycosylation and glucose metabolism is essential for developing precision medicine approaches to manage diabetes and related complications.