I was reading this question and it got me thinking about what a person's "original lifespan" really was.

Does the original lifespan mean the amount of time a person has from birth to death, ultimately caused by old age (e.g. the longest a person could live barring abnormal health problems or unusual circumstances (e.g. murders, accidents))?

What if the person contracts a lethal disease? Surely it would shorten their lifespan, but would it affect their original lifespan?

So, take for example: John has a lifespan of 93 years (as seen through Shinigami eyes). He works for the CIA, though, and at one point comes into contact with a high dose of radiation from a nuclear device. Doctors tell him he only has a couple days to live.

In this case, John's lifespan has been shortened from 93 years to 2 days. If he writes his own name in the Death Note, set to die from a different disease that takes years and years to develop, would he have effectively beaten radiation poisoning?

Note that the 23-day rule (XVII) would not apply here thanks to rule XVIII.

  • Only the Death Note can change a person's lifespan. Therefore John will not come in contact with high radiation, he might not even be able to become a CIA member, since they probably wont live 93 years. Aug 16, 2014 at 6:44
  • @PeterRaeves I'm not sure what you mean. John becoming CIA/being exposed to radiation are things that already have happened and have nothing to do with the Death Note. If your statement "Only the Death Note can change a person's lifespan" were true, that means everyone would die from old age, and never from disease (etc) unless specifically written as the cause of death in the Death Note.
    – empire539
    Aug 16, 2014 at 19:35
  • Misa's time of death, as mentioned in the answers, is a clear indication that a person's time of death is predetermined. Exactly how it happens, and the life they lead up until then, is not singled out as determined. However, to suppose that the time of death was preordained, only to be usurped by happenstance, seems silly. His time of death is at age 93, and is only shown to be alterable by a death note. Your hypothetical is either in clear conflict with the basic principles, or is a fanfic that is supposing mechanics never indicated or established in the source. Aug 17, 2014 at 1:37
  • anime.stackexchange.com/a/11424/8024 The first part of this answer seems otherwise germane. Aug 17, 2014 at 1:46
  • @zibadawatimmy Hmm... just to clarify my understanding of your comment: if a Shinigami sees that a perfectly healthy, newborn baby only has a lifespan of a few days, does that mean the baby absolutely will die within a few days, presumably due to some external cause (e.g. a car accident; not counting the Death Note)? I was under the impression that one's lifespan was as defined as in the question, hence my confusion. If you can provide more sources (e.g. quotes/events from the manga) in addition to Misa's, please elevate this to an answer.
    – empire539
    Aug 17, 2014 at 1:52

3 Answers 3


The original lifespan is the time you are supposed to have alive at the moment of birth, unless someone, Shinigami or human, use their Death Note on you, or you make a deal with a Shinigami shortening your lifespan, or a Shinigami sacrifices themself to allow you to live incrementing your lifespan.

What if the person contracts a lethal disease?

Once you spent your lifespan you will die, the reasons of death doesn't matter. If you contract a disease you will live until your lifespan allows you to live.

To illustrate this, Amane Misa was supposed to die when the fan attacked her. Gelus knew her life will end, and decided to intervene. Since her lifespan was spent and she didn't die when she was supposed to, Gelus dies transferring his lifespan to Misa, hence she no longer lives with her "original lifespan" but the shinigami's.

would he have effectively beaten radiation poisoning?

He could be died because a indirect effect of the use of the Death Note, which caused him to be affected of radiation poisoning, as can be seen in this other answer, but if there isn't Death Note involved, no matter what he should die when their lifespan exhaust, so he could just get lucky and not being poisoned or something happened before hand that prevented him from being poisoned.

  • 1
    Can you clarify your last sentence, "One way or another he may avoid radiation poisoning since it will cut short his lifespan"? Did you mean that he'll die from radiation poisoning regardless of what's written in the Death Note (where the time of death is beyond two days' time)? If someone wrote him to die in 1 week from a heart attack, he would still die in two days of radiation?
    – empire539
    Aug 16, 2014 at 19:42
  • Also, can you provide a source (e.g. one or more of the known Death Note rules) which support your answer?
    – empire539
    Aug 16, 2014 at 19:42

I think you are missing the point of "Death Gods". The "original lifespan" of a human is the amount of time they have from birth to death. And I think it is already decided from before!

The only way it would change would be any type if interaction with a death god/death note being introduced to the situation.

So if he got affected by radiation, and were to die, this would have been taken into account in your original lifespan! (As long as the radiation situation was not introduced by someone with a death note or a death god!


Okay, let's say I have a Death Note. Now, another Death Note owner wants to kill me.

Let's say to save my life, I write my own name in the Death Note with bradykardie as a cause of death. I will over 23 days. And when my lifespan ends I will die of bradykardie. So, that means, if no Death Note is involved that CIA Agent won't die, because he isn't supposed to die then. But if he writes his own name in the Death Note, with a disease as a cause of death, he will die of that disease when his lifespan ends.

  • The CIA agent is already dying of radiation (no Death Note involved). I'm asking: if he uses the Death Note to write that he will die of another disease (that takes longer to develop than 2 days), will he die from the radiation, or will he die from the disease? Also, please support your answer with a source.
    – empire539
    Aug 16, 2014 at 21:38
  • The original lifespan can only be shorten by a death note. But let's say, he is destined to die of radiation, he will die of radiation, because the death note can't prolong the life of someone.
    – DarkYagami
    Aug 17, 2014 at 8:07

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