Well let me give you an example. If for the last 8 weeks you took 8000iu of Vitamin D3 and now have a level of 60ng/ml, then you need to keep taking 8000iu. If you took 5000iu then you need to take 5000iu.The key is the 8 weeks. Whatever level you reach, it should not continue to rise with whatever amount you are taking. (Getting correct sunshine, though, will make it rise higher.) Most people need 5000iu to reach 50ng/ml but it is not a guarantee.