My doctor told me that Vit D deficiency can contribute to muscle weakness, fatigue, mood swings, depression. But, I was severely anemic too, (and still am but not as severe) so I couldn't tell you if my symptoms were more due to the anemia. I'm sure there is an overlap.
I know that before my blood transfusion, I felt way "off", and I knew I needed "major tweaking". But I didn't know what. After the transfusion, I feel TONS better, but I knew I still was not 100%. That was when the Vit. D deficiency was discovered, and that I'm not nearly as anemic as before, but still anemic. My mood swings and depression virtually disappeared overnight.
I expect that in about 2 months, after building both my iron stores and the Vit. D, I'll just feel even better.
I'm paying closer attention to how I "feel" and honestly I feel like everyday, I get better and better, not just physically but mentally and emotionally too.