I have M.S. I started feeling crappy again. Tired all the time sleeping 12 -14 hrs, muscles hurting, twitching (which I assumed was all the m.s. til I read more about vit d). "Brain fog" increased, constipated, upset stomach, increased migraines.  My neuro's office called today. Vitamin d level DOWN AGAIN. Should have known. Earlier this yr went to family dr. told him how I felt. Had read an article sounded like me, I asked them to do a vit d level. Came back 18, was told take vit d over the counter. Right> Got worse down to 9, then finally was given 50,000 units 1 x weekly, no side affects, took almost 2 1/2 mths to come back to 66. They never gave refill or said keep taking, soooo I didn't.  Well when the crap hit again, I asked Neuro about d level, they did the test, which they told me today 20.3.Back on 50,000 units, am going to question big time why the drop. Especially after reading bout problems low vit d causes.SCAREY