Overweight and obesity are extremely complex disorders, that combines genetic predisposition, changes in hormonal levels and horrible obesogenic environment that we have nowadays. There is no simple answer on how to lose weight as it depends on multiple factors too - your home and work environment, availability of stores with fresh products, your medical history, your goals in general. What is working well for one person, may not be ideal for others or even sometimes dangerous (depends on other comorbidities).

Most important part is not just to lose weight, but do it safely and maintain the weight loss. For that you need a whole lifestyle change, that is why it is so hard for many people. The major rule is: permanent dietary changes needed for a weight loss and regular exercises needed for maintaining the result.

My advise (if you are in the US) - find an obesity clinic with obesity board-certified physician, discuss all your concerns and develop a plan what will work specifically for you. It is pretty well covered by insurances and you will always have a specialist who can answer your questions and help to overcome any barriers in the future.

And remember we all are just internet strangers, take all our advices with healthy skepticism.

Let me summarize some correct facts prior to answering your question:

• Vitamin D is indeed lipid-soluble vitamin, therefore it is only comes in capsules with oil or in liposomal form.
• Absorption under the tongue (sublingual absorption) is amazing for water-soluble medications, however works for lipids in lipisomal forms too.
• Any fat soluble vitamin can cause overdose in large quantities (unlike water-soluble), however therapeutic window for vitamins usually is pretty large. Therapeutic window is the dose range that can be safely taken without significant risk of overdose. Specifically for vitamin D, your recommended daily dose varies between 1000U and 5000U (depends on the season, place of living and your ethnicity). For severe deficiency we can prescribe 50000U weekly for a couple months. To overdose you need to take much more - more than 10000U daily for a few weeks.

Now to direct answer to your question - you are not missing a lot:

1. Yes with no optimal sublingual administration, absorption could differ. Bu it is not a chemotherapy, it is vitamin D - difference in health benefits if absorption dosages slightly inconsistent is minimal.
2. Whatever was not absorbed sublingually will be absorbed later in your GI tract.

Basically, don’t overthink it. And try not to ask health advice from internet strangers, better talk with your primary doctor if you have any concerns.