Cholesterol binding meds? If this is the correct term, these drugs are like magnets and bind lots of things to them.

What is the name of this medication?
Questran and Colistid and Welchol are examples.

The statins chemically block cholesterol and are different. If you are on a statin, there should not be much or any effect on B12.

Nexium and other acid reducing drugs do lower B12 however.
They also block iron absorption too. (and folate, and calcium and zinc, and magnesium and some other trace minerals).

Oral B12 must be taken on an empty stomach or else it won't be well absorbed at all, lost in the food present.

Eating low fat reduces the chances of getting enough Omega-3's which are needed by the nervous system. Today most low fat diets have been discarded because they do not support normal physiological processes needed for health.

Do you have pernicious anemia? That is a lack of intrinsic factor. If this factor is gone, due to autoimmune attack on those cells that produce it, you will never get B12 from food, and will always be low. So establishing a good oral habit and dose --5mg would be best-- can keep you normal and avoid the shots.

If you have low stomach acid, and are not absorbing iron, you would feel quite ill. Loss of the other nutrients I listed here, also contribute to feeling ill. B12 is not the only nutrient affected by low stomach acid.