Prediabetes: diagnostic aspects, clinical features, and emerging therapeutic opportunities, with a focus on Vitamin D

BACKGROUND: Prediabetes is a highly prevalent and heterogeneous condition associated with an increased risk of type 2 diabetes mellitus (T2DM), cardiovascular disease, and other cardiometabolic complications. Growing evidence suggests a potential role of vitamin D in glucose metabolism and diabetes prevention. OBJECTIVE: To provide a clinically oriented interpretation of the available evidence on epidemiology, pathophysiology, clinical implications, and management of prediabetes, with a specific focus on the rationale and evidence supporting vitamin D supplementation in individuals at increased metabolic risk. METHODS: A multidisciplinary panel of Italian experts in endocrinology, diabetology, and metabolic diseases reviewed current guidelines, epidemiological studies, randomized clinical trials, meta-analyses, and recent consensus statements addressing prediabetes and vitamin D. RESULTS: Prediabetes is a dynamic and potentially reversible condition characterized by heterogeneous trajectories of progression, persistence, or regression. Lifestyle intervention remains the cornerstone of prevention. Vitamin D deficiency is common among individuals with prediabetes and may contribute to insulin resistance, β-cell dysfunction, inflammation, and endothelial dysfunction. Clinical trials and meta-analyses suggest that vitamin D supplementation may reduce the risk of progression to T2DM and increase the likelihood of regression to normoglycemia, particularly in individuals with vitamin D deficiency or high metabolic risk, although treatment effects remain heterogeneous. CONCLUSIONS: Given the growing clinical and public health burden of prediabetes, early identification and personalized preventive strategies are needed. Current evidence supports consideration of vitamin D supplementation as a complementary intervention in selected high-risk individuals with documented deficiency, while further studies are required to better define optimal treatment targets and patient selection criteria.