Reply To: Hi, I started taking Vit D3 back in the spring when I found my level to be 25ng/ml. I started with 5000 IU of D3 for a month and retested. Low 40's, so switched to 10,000 IU for a month and got it to 52. Switched to 15,000 IU and have now overshot to 102. I have reverted to 10,000/day. Should I stay there for a month or go to 5000 IU immediately? I don't really notice any side affects other than I may be waking about an hour earlier than I used to. Other than that, I love how I feel in general now. No more afternoon snoozes needed.