I have lupus. should i take vitamin d, since i can't be in the sun?

Yes: Vitamin D deficiency is quite common. Low levels detected on blood tests are often treated initially with Rx Vitamin D supplement taken once weekly for six weeks, with re-measurement of the level shortly afterwards.

You can.: It is genrallly not needed if you are eating a normal diet and using vitamin supplements as you have noted. If you feel you must have your doctor order a vit d level first.