i too have low vitamin d levels i dont know exactly how low but i have only been given supplements for a month 2 start with after 2 weeks of taking them i have had muscle weakness in arms and legs although i have suspected rheumatoid arthritis also how are your levels now?
I have similar symptoms, which is what prompted my doctor to test my vitamin D. She said low vitamin D can cause fatigue and muscle fatigue and soreness, as well as joint pain, tingling in hands and feet and a host of other things. My vitamin D level was 15. I too was prescribed 50,000 IU but only once a week for 2 months and then I'll be retested.
If you do an internet search for "low vitamin D" you'll find some very good info on symptoms, etc.