Depends on whether "not doing a great job" is based on actual labs (ALT/AST/GGT) or just a gut feeling, those are different problems. If it's real elevated numbers while on cycle, the fix is usually addressing the cause (dropping orals if you're running any, since those are the usual liver stressors) rather than layering a supplement on top, and it's worth actually flagging to your doctor rather than self-treating. If you're picking between the two anyway, TUDCA has better research behind it for actual liver protection than milk thistle, which is mostly weaker antioxidant-based evidence, but neither one is a substitute for figuring out what's driving the numbers in the first place.