Hello, I have also had low Vitamin D and my rheumy put me on the high prescript
ion dose of Vit D and after while - around 1 month it came back to normal. I don't think is true that it is not reverable...
Now my vit D is normal but I still take the it in pills just normal daily dose.
I was also low in Iron and needed to start to take all vitamins daily.
Good luck to you!