Maybe there's another (mod free) way to do this, I don't know, but I had to enable health bars for friendly NPC's to be able to pay attention to my clannfear pet's healthbar.
Problem is, there's only an "on" and an "off" option, and no "injured only" option like the other health bar categories have. Thus, the result is that I run around seeing green healthbars over the heads of every single NPC in the game (previously I had mob health bars on in cluttered areas so I could more easily see where they were and not accidentally run into the middle of them), and it's a bit immersion breaking to run through a town and see green stripes everywhere.
Could we please have an Injured Only option for friendly NPC's as well? That way the same option would be useful not only for people with pets but also during escorts etc.