on 

there is a great stephen king short story, “survivor type,” about a med student who is the sole survivor of a small chartered airplane crash on a microscopic island with absolutely no food or water anywhere on it. he’s not a good guy; in fact the purpose of this trip was to deliver a big package of heroin to a buyer

he tries as he might to catch the rare fish or bird, but it’s way too little, too few. in one last-ditch attempt at a seagull he breaks his ankle very bad. he decides the only way to not get blood poisoning is to amputate the foot. luckily he has all that heroin to use as painkiller, so he takes enough to deaden the pain of self-surgery, but not enough to lose consciousness

he then realizes he has a limited source of food it would be a shame to squander

obviously the story doesn’t end well, weeks later. go find this story and read it, it’s pretty well-told and creepy but not good before dinner