Many years ago my level of Vitamin D was checked and the doc stated that they'd never seen such a low number. I started taking Vitamin D3 daily--about 2000u/day. He hasn't checked the levels since so I don't know where I am now. This test was performed when I was rarely outside before I was exercising. With my walking and now cycling and taking D3, I'm sure my levels are quite high. I haven't asked for another test and since I ride at the crack of dawn, or before dawn usually, I'm still going to take the D3.