You're unusual in your supplements in that many of them (not all) have potential benefits or are clinically relevant to you.
Vitamin deficiency following sleeve gastrectomy is known so continuing your vitamins is both a good idea and won't impact treatment. A mutli B (not just B12) and vitamin D are best.
Milk thistle contains silymarin and there is some evidence it may help untreated patients
But, there is also some evidence it does not do anything much
While I suspect it should not interact, the best treatment for HCV related liver disease is to get rid of the HCV so stopping milk thistle during treatment avoids any worry of interaction. The major benefits are flowing from the DAAs. You can continue it after, but after treatment, you'll find your liver enzymes are normal and you can't get better than that - the cause is gone so...
In general, as far as your body is concerned, collagen and gelatin are just different forms of protein. They will be digested in your gut into their constituent amino acids and from there do no more, no less than eating a little chicken, red meat or fish. I'd rather have the real food myself, it's tastier and more natural.
That said, undenatured type II collagen (UC-II) is not intended to be used by your body as a collagen re-builder. In a process called oral tolerance, very small doses of UC-II are taken to train your body’s immune system to stop attacking its own collagen
Here is a vox pop on it:
And here is a medical literature review suggesting a net benefit:
So UC-II in low dose would be a probable yes. It should not interact with DAAs.
With Chondroitin/Glucosamine there is some weak evidence they may help. I certainly have patients who say they benefit. Here is a review:
So I'd suggest that while on the treatment:
- You should take the B complex + Vitamin D and it won't interact.
- I'd skip the Milk Thistle for now and don't think there is going to be a reason for it after.
- General collagen and gelatin are no better than fish/meat based food which is natural and tastier.
- UC-II collagen at low dose may be useful and won't interact.
- The chondoitin/glucosamine are fine to continue, probably beneficial and won't interact.