My D was low and I'm now taking 5,500 IU of D3 a day. I do have less pain than before. It didn't get rid of the pain but helped ease it. I also have more energy, too. My doctor knows how much I'm taking and we periodically check my D levels.
Because of my low D, I wasn't absorbing calcium and now have osteoporosis. I started taking calcium years BEFORE menopause just to prevent osteoporosis but didn't realize my D levels were so low. Now I have to take medication for that, too. Bummer!
Vitamin D is an important vitamin. We aren't in the sun like people used to be and, when we do go out in the sun, we wear sunscreen so we still aren't getting vitamin D. There are very few food sources for D, also. So, I take the supplements. I have read that adults should take 2,000 IU of D a day but be sure to talk with your doctor first. For the newbies, there is a link all about this in Fibro 101.
Sherrine