I do have a liver function test every year as I continue to take Zetia but the recommended dosage of Niacin does the trick for me.
I doubt I would personally worry unless I got up above the 10 gms/day level or so, but that’s just my opinion.
But more and more these days, vitamins and therapies and new meds are targeting liver function. Like the statins.
So it’s always a good idea to consult your doctor.