Vitamin D Supplements May Improve Blood Sugar Levels If You Have Prediabetes

Verywell Health•January 8, 2026•health

Key Points:

Vitamin D supplementation may help some people with prediabetes return to normal blood sugar levels, increasing the likelihood by 27% when combined with regular exercise and a balanced diet.
The vitamin improves insulin secretion by pancreatic beta-cells and may reduce inflammation linked to insulin resistance and impaired glucose uptake.
Clinical trials used an average daily dose of about 4,300 IU, exceeding current general recommendations, and the Endocrine Society in 2024 suggested higher doses for high-risk adults with prediabetes to prevent diabetes progression.
Experts caution against megadoses above 5,000 IU per day due to unknown long-term safety, and warn that excessive vitamin D could cause hypercalcemia, leading to bone, kidney,