Nice to see more benefits of Vitamin D. Highly recommend the supplement for tech workers who spend a lot of time indoors. I take 125mcg/5000IU a day when I wake up and it's subtle, but I just feel a little better with it. Sports Research is a good brand (not affiliated). Nothing better than getting some real sun though, especially in the morning.
Also, ask your doctor to get yours tested! A couple years ago, my D was on the low end (31.7ng/mL; 30-100 is normal). I've been taking 5000IU of D3 since then, and a lab last month had me at 59.1. That seems to be about the perfect dose for me, and it's dirt cheap.
BTW, did they tell you to back off or cut your dose? at 59 ng/mL you're in the danger zone.