The best way to get personalized recommendations for vitamin D intake is to work with your healthcare provider, who can check your vitamin D status and periodically monitor changes in blood levels with supplementation to achieve adequate blood levels of 50 nmol/L or more.[1]
However, in the absence of pressing health issues, most people are not likely to monitor vitamin D levels with regular blood testing, and much research has been conducted to correlate vitamin D supplementation doses with blood levels achieved in various populations.
Approximately 1000 IU of vitamin D3 a day is needed for half of the population to reach a blood level of 75 nmol/L,[2] and an estimated 95% of the population will achieve this blood level with 1700 IU/day supplementation.[3] Taking the current body of evidence into account, 1000-2000 IU of vitamin D3 per day seems to be sufficient to achieve adequate vitamin D levels for most of the population. It is important to note that a healthcare provider may initially prescribe much higher doses to resolve a vitamin D deficiency.