25,000 IU of Vitamin D is recommended for those whose 25(OH)D3 levels are extremely low, and is helpful for those who have difficulty complying with a daily dose. One capsule two or three times per week may be recommended for a short time to increase blood levels to a healthy range. Monitoring serum calcium and 25(OH)D3 levels is strongly recommended to prevent toxicity. This formula also contains Vitamin K-2, which research has shown to be an essential nutrient for promoting bone density and proper bone nutrition. Click here to purchase the safest Vitamin D on the market in the USA.