So, I'm on the fence about this question and would appreciate other opinions myself.

So, between food, per modum cibi and medicine per modum medicinae, "vitamins" and various nutritional supplements sit in a gray area as far as I'm concerned, where they're kindof related to food/nutrition and kindof medicinal, supplementing things your body needs due to deficiencies in one's diet, as there are many health conditions, including some severe chronic ones, that can result from deficiencies in certain types of vitamins.

I believe that the intent of taking dessicated liver capsules would be to get the rich vitamins and other things in there that come with it.  So my personal inclination is that it would be OK, especially since in its capsule format, it's barely resembles food and doesn't seem like it's consumption per modum cibi.  You take it in the manner of medicine, where you just consume/swallow it without really chewing, etc. as you would in eating a meal.

So I'm on the fence but leaning toward it being OK ... pending citation from some approved theological source on the matter.  I'm guessing that pre-Vatican II, things like "dessicated liver" supplements for vitamins and health were probably a rare thing and not addressed by the theologians.  As Bishop Sanborn said in one of his catechetical talks, there can be a variance of opinion, not so much on principles, but the applications to principles, especially to changing circuмstances, and society has changed so much since Vatican II, combined with a vacuum of credible approved theological sources, it's probably a bit up in the air ... unless someone could find a pre-V2 source that addresses it.

I think if it’s medically necessary it would be ok . I take armor thyroid ( porcine) and am not worried about violating the fast.

Right, that's where some substances are on the fence between medically "necessary" and nutritional supplement.  Then, of course, HOW necessary should it be?  Would I have to be risking death not to take it, or just some subtle compromise of my overall health?

I don't think that this one is that easy.  Thyroid would definitely be medically necessary.

Given that swallowing a pill to me sounds more like ingestion of medicine than food, per modum cibi, I'm inclined to think it's OK if there's any reasonable need for it ... but the I would give my "opinion" a 60% of being the right one, so barely on one side of 50-50.