[UnwashedPeasant]

"So if I walk into a drugstore, do I just buy a bottle of "vitamin D" in some dosage that I can add up to the recommended, or is there some other qualifier or special form it should be in?"

Get D3. For best results, get the spray version from L.A Naturals brand. It has 180 doses of 5000 iu for $20 retail. I think you squirt it under your tongue. It is the best absorbed and the cheapest. It is discounted to about $11 on Amazon.com.

[diamond6]

ping

[UnwashedPeasant]

Vitamin D3 should be taken with vitamin K2.

Here is a very cheap source of D3 with K2 included, and it is kosher:
Sublingual D3 at iherb.com