If someone with advanced knowledge that a blood transfusion would save them and refuses then suicide might be appropriate for cause of death..
Years ago, before HIV was identified, a lot of doctors thought that they knew that a blood transfusion would save a patient wound up killing them. Also, a lot of people wound up getting infections in their liver from infected blood resulting that they die a slow torturous death. A lot of these people did not actually need blood and those people would have been saved if they would not have gotten blood transfusions. From a medical position BT had risks and still do, but if death is imminent without one then a patient has no choice if he wants to live, or at least have a fighting chance.
From a JW position, the position is religious. Medical risks are reasons JW give to support their religious position and to show and persuade non JW that their religious position is not fanatical, but also to convince JW too of the reasonableness of the stand, never-the less, even if it was possible to administer 100 percent safe blood without any risks whatsoever to a JW, a JW could not accept.
If a JW knows for a fact that God does not want him to take blood as the WT teaches then the JW is obeying God when he refuses a blood transfusion or refuses anti-venom or certain vaccines,...etc. But if it came down to it and his refusal of blood carried a risk of probable death and he did not know for a fact that God did not want him to take blood as the WT teaches and he refuses because of what he believes the Bible is saying from how the WT interprets the Bible, then his refusal is in obedience of the WT if he is refusing for religious reasons.
In survival situations a person may have to eat rat or roaches or snakes or human flesh, etc. Some people would choose to die. In some situations when a person is threatened unless they submit to the demands of their captors, some people would also choose to die.
JW are conditioned mentally to disgust blood but to the average joe that never gave it a thought, do not feel any repulsion to have quarts or gallons of some dude's bloody blood and dna and fluids, etc transfused into their body.