I am still have having horrible MS but also have been feeling REALLY tired. I'm 15 weeks now and my doctor said I should not be feeling as tired as I am. My muscles are weak and I feel so drained of energy 24/7 and it doesn't matter how much sleep I get. She checked my thyroid and my vitamin D levels and my vitamin D levels were low. I'm on 4,000 IU's daily for 8 weeks than 2,000 IU's daily after that. I never knew that vitamin D had to do with you being tired or weak but she said it does. If anyone had this happen how long did it take to get your energy back up. So far I have been taking it for a week and I'm not feeling any different.