The best research at the moment shows that in order for humans to be healthy, they need a minimum blood level of 40ng/ml. At levels below this and the incidence for cancer and autoimmune disease rises “dramatically”. Here at the VDC we promote a level of 50ng/ml. To reach this level it takes the average person weighing 150lbs taking 5000 iu a day. This is what we promote. Some other studies have shown that 5000 iu should be increased to more like 6-8000 iu. If pregnant you should probably take at least 6000iu but some other studies have shown that 10,000iu a day could be optimal. If you weigh more you have to take more.Of course if you are already in a “diseases state”, no one knows how much you may have to take to get better.