Drugs used to treat illness, are all studied by bioavailability before the FDA will consider them for approval.

Changing the diluents can change the rate of absorption of a drug.
Dilantin is a good example of this. There is alot of information on it because the Brand name was made with a diluent that REDUCED the rate of absorption. When generics tried to match the Brand name data, they could not. So for a long time Dilantin was alone on the market. But now that problem has been solved, and a few generics do exist, and have the name "delayed action" attached to them.

Because these studies are expensive, most supplement makers do not do them.

But I did find this one that is recent:
http://docs.google.com/viewer?a=v&q=...HnnaNdoqV88xEA

In general sublingual products are swallowed, and absorbed in the GI tract as well. They tend to be more expensive than other formulations too. You'll notice that drugs we use are not commonly made into sublingual forms. That is because it is quite difficult to get reliable data about rate of absorption this way. (this does not include "melts" which are also swallowed and used for people who may not be near water to take an emergency dose).

I don't think sublingual is necessary for D3. This article supports that opinion. But since the oral forms are in the form of micrograms (the units seem high but the actual dose is in micrograms), taking on an empty stomach like with B12 and other drugs given in micrograms, will help with absorption so the tiny amounts are not lost in food.

So the bottom line is no, I don't think it is necessary to take it sublingually. Your choice of manner is up to you however, since D3 appears easy to absorb from the study given above.

edit to add: One further search brought up this brand name company making claims about micellized D3:
http://docs.google.com/viewer?a=v&q=...JQqz1CFvC9wxHw

I am unsure if this pertains to the data found in this study:
http://www.ncbi.nlm.nih.gov/pubmed/16902814

This explains what micellized means:
http://vitamins.lovetoknow.com/Micel...iquid_Vitamins

Given the first study I put up here showed good absorption, I don't really think an expensive version is really necessary, adding considerably to cost. Vit D3 is not an expensive item to begin with.