Hi Lisa....     I to have M.S. and just like you my Vitamin D levels are very low... This is the third time in the past 6 to 8 months that I have been put on 50,000 IU I will have to take it for the next 2 months then I have to go back and take 2000 IU until my levels are better.... I have done some reading on M.S. and low vitamin D levels and there are more than you think that have the same problem.... I guess it is just in our future to take higher levels of vitamin D for the rest of our lives.... All I know it is going to get expencive cause as you know medicare or medicaide do not cover this drug... Oh well I guess the only ones that can really afford M.S. is the rich.... lol... I do feel better after I take the extra vitamin D but when I'm low on it I have fatigue all the time... I wish that they can find out why and fix the problem...