Witcher channel asks for sign ins due to age so using the IGN vid atm, if anyone knows of a way to archive this or whatever please go for it.
https://www.youtube.com/watch?v=yWMu6JeT2g8
Some 4chan thoughts on the matter.
https://boards.4chan.org/vrpg/thread/3675650/witcher-4
c/Gaming thoughts on the matter.
https://communities.win/c/Gaming/p/19A0ojiz4R/witcher-4-ciri-the-girlboss/c
It happens at least twice in 3, or can do. The first time players encounter it is when talking to the bootynist, I mean, the botanist at the start in White Orchard when Geralt offers the use of Swallow to try and heal someone. The two outcomes are either you don't offer the potion and the person dies, or you do but it renders the dying part catatonic so not much better.
There's a second time in Skellig when Geralt finds a note belonging to someone who looted a witcher's belongings and drank one of the potions. It kills the looter.
The white orchard one I was referring to, maybe the botanist's skill lessened the damage of the potion so it wouldn't kill her but not enough for her to fully recover. But hell witchers have to be careful of the toxicity of their own potions.