I'm recovering from a Vitamin D deficiency. My levels (acording to my endo) were 16.. I was supplementing with 6-8,000 IU of D3 daily. I was told that my serum levels have gotten up to 70, but unfortunately I'm still exhibiting a lot of the same symptoms.. Brain Fog, Fatigue, LOW T (no libido), proximal muscle fatigue, etc...I'm trying to find out how long it's going to take for me to start feeling better again.. Vitamin D deficiency is a nightmare!