From what I understand it’s pretty hard to get a vitamin D deficiency unless you stay indoors all the time. Ultra-violet light on your skin causes vitamin D to be created. But corticosteroids (such as Cortef) can hamper the bodies ability to absorb vitamin D. The RDA (recommended daily allowance) of vitamin D is supposed to be met with 30% skin exposure for 30 minutes at moderate latitudes. It’s summer. Wear something light and take a couple of longs walks during the day, see if that does the trick. You might also find a full spectrum light bulb (I got one at Wal-Mart, for not very much) to put in a frequently used place. I’m not sure how well that will help, but it certainly wouldn’t hurt.