From what I've seen of yt vids, reddit threads, etc.; toxicity starts reducing hp once the toxicity points have surpassed 70% of the maximum points. Currently, my toxicity level totals 153 points, which should allow me to consume at least 2 decoctions (adding up to 100 toxicity points) remaining below the 70% limit (which is 107.1 out of 153 toxicity points), yet I'm somehow still losing hp.
The game does a piss-poor job of explaining this feature and I really want to understand it so I can use it better. If anyone's got info or sauce to explain what I'm not getting, I'd greatly appreciate the assist.