Vitamin D is becoming the wonder drug of the decade. The more we learn about the functions of vitamin D, the more we want people to have adequate levels in their blood. There are some data suggesting that low vitamin D levels are associated with more active RA. However, the only real way to know this for sure is in a double blinded placebo controlled study in which vitamin D is compared to a placebo. We are one of the institutions looking into this. Anyway, yes, it is possible that you are feeling better because your vitamin D levels are up.