Reply To: I am a 52 year old male. I went to my doctor complaining of not feeling well and staying tired all the time. He checked my testosterone level and my vitamin D. My testosterone came back low (238) and my Vitamin D came back low (17). We have decided to not do anything with the testosterone for now. I am taking my vitamin D3 2000iu twice a day for now. How long should it take for me to start feeling a difference. Also what all kind of differences should I see?