No need at all IMO. i have had bloods done when on cycle with orals and liver values have never been out of line.
got then done recently after a 16 week prep which included dbol at 40mg per day in the earlier stages and var at 100mg per day in the latter. had stoped var day of blood tests had been 50mg the week before them and liver values were fine.
havnt took milk thistle or any other liver protector for a long time.