Carlson Vitamin D3 1,000 IU (25 mcg) is the preferred form of vitamin D that's important for promoting strong bones, supporting immune system health, and helping to regulate calcium and phosphorus metabolism. Higher levels of vitamin D3 in the blood are associated with strong bones and good health, as well as a strong immune system. Each soft gel provides 1,000 IU (25 mcg) of vitamin D3.