More than one in three Americans is prediabetic, meaning that roughly 96 million people have higher-than-normal blood sugar levels that raise the risk of developing type 2 diabetes, heart disease, and stroke if left unmanaged. While vitamin D supplements may offer a slight benefit for blood sugar control, taking then isn’t the most effective way to significantly improve glucose levels.\n<\/p>\n
Vitamin D plays a role in blood sugar regulation by supporting insulin sensitivity<\/a> and secretion and by lowering inflammation, which can interfere with insulin signaling in the body. Notably, prediabetes has been linked to low levels of vitamin D.\n<\/p>\n Research examining how vitamin D supplementation may affect prediabetes has shown some promise, said Roxana Ehsani, MS, RD, CSSD<\/a>, a sports dietitian. One 2025 study found that people with prediabetes who took a vitamin D supplement for three years were 30% more likely to return to normal glucose regulation when compared with those taking a placebo.\n<\/p>\n Other research suggests supplementation decreased the risk of progression to type 2 diabetes<\/a> from 25% to 22% over three years, said Anne Cappola, MD<\/a>, an endocrinologist and professor at the University of Pennsylvania’s Perelman School of Medicine in Philadelphia.\n<\/p>\n Still, it\u2019s important to note that there\u2019s no medical consensus on the optimal dose of vitamin D for this purpose. It\u2019s also unclear if there are any adverse long-term effects of taking vitamin D supplements.<\/p>\n While the risks of vitamin D supplementation are generally low, it shouldn\u2019t be the main focus of diabetes prevention, Cappola said. Research hints at only small improvements in blood sugar, and vitamin D is a \u201cmuch weaker\u201d intervention compared with lifestyle factors like a healthy diet and exercise.\u00a0\n<\/p>\n “Lifestyle interventions reduce the absolute risk of progression from prediabetes to diabetes by 15 percentage points over three years,\u201d Cappola said. \u201cI do not want vitamin D supplementation to be a distraction.”\n<\/p>\n