How often should you have your vitamin d level checked?

Precise recommendations are somewhat controversial, but knowing that this is a "fat soluble vitamin", indicates that any change of Vitamin D-3 intake should be checked no sooner than 3-4 months following supplementation. Thereafter, would not need to check more than once yearly, in my opinion. Some dosing recommendations include adding 800 units daily, and a desirable goal at 50-70 ng/ml level.