1000 IU (25 mcg) per day increases vitamin D blood levels 10 ng/ml (25 nmol/L). 2000 IU (50 mcg) per day increases vitamin D blood levels 20 ng/ml (50 nmol/L). If the vitamin D blood test was 30 ...

Most people who supplement take between 800 IU and 2,000 IU a day through either a multivitamin, Vitamin D capsule or a combination of both. Vitamin D3 is preferred because it absorbs better than D2.