Concur - I was diagnosed with vitamin D deficiency and my doctor prescribed an initial regimen of prescription tablets at 50,000 IU and then suggested 3,000-5,000 IU daily.
Might also depend where you live. My doctor did as yours, but I live in northern New England where we don't typically expose our skin to the sun for months at a time. Perhaps doctors closer to the tropics assume at least a low level of sun exposure?
Yes, and I'm saying that this does in fact happen.