Vitamin D deficiency treatment is not going to immediately relieve pain. Over the coming months as your bone health improves, you should start to feel better. In the mean time, "hip" (when someone says hip pain, that sometimes does not mean the actual joint) pain while walking on a treadmill could improve if you slow down and use both handle bars to help support your weight. In turn, while walking off the treadmill, you should try using a walking stick, cane or trekking stick in the opposite hand, opposite of your hip pain. When you are in "stance phase", standing on the painful side, then some of your weight should be distrubuted to the opposite hand into the assistive device. A physical therapist should be able to help you work this out to improve walking comfort. 

Dr. Christina Lasich, MD