Apocarteresis in Buddhism Apocarteresis is a form of suicide where a person stops taking food and/or water.

Now, I want to make it very clear that I have no intention of committing suicide anytime soon.

However, as the Buddha taught, old age, illness and death are part of life.

I believe that the most dreadful thing is not the disease itself or even death, it is my experience that in some countries (for legal reasons) doctors will insist in keeping patients alive when it would be compassionate to let the disease take its own course.

I am relatively young now, and healthy. Again, I have no desire to die soon.
However, having witnessed my grandfather's unnecessarily protracted death, I would rather not leave my life in the hands of overzealous doctors come the time. On the other hand, I would want to avoid causing suffering and accumulating kamma with an unskillful act of death.

How is apocartheresis as a form of euthanasia viewed within Buddhism in cases of terminal illness?
Your calling it "suicide" (i.e. intentionally killing yourself) and "committing" (a crime) suggest that the action/intention/view you have in mind are not appropriate.



The following paragraphs from pages 82 and 83 of this Vinaya commentary,
The Buddhist Monastic Code I: The Patimokkha Training Rules Translated and Explained, by Thanissaro Bhikkhu suggest that the doctors would not be "killing" is they withhold treatment:


  Inaction. Given the Vibhanga’s definition of taking life, we can infer that
  inaction does not fulfill the factor of effort here, for it does not cut off the life
  faculty. Thus if a bhikkhu sits idly when seeing a flood sweep a person
  downstream, he commits no offense—regardless of his feelings about the
  person’s death—even if the person then drowns. Recommending that another
  person sit idly as well would also not fulfill the factor of effort here, because the
  category of command covers only the act of inciting the listener to do any of the
  four actions that would fulfill the factor of effort under this rule.
  
  Medical care and life-support. The same holds true if a bhikkhu decides not to
  give a patient a treatment—or to discontinue treatment—that might conceivably
  extend the patient’s life: It does not fulfill the factor of effort, for such acts do not
  cut off the life faculty. At most they simply allow it to end on its own. The Canon
  supports this inference by treating such actions not under this rule but under
  Mv.VIII.26.3-4, where it imposes only a dukka˛a on the act of refusing to give 83
  any treatment at all to an ill bhikkhu, or of discontinuing all care for an ill
  bhikkhu prior to his recovery or death. This shows that the compilers of the
  Canon did not regard these acts as cutting off the life faculty. (Mv.VIII.26.8 lists
  the ideal characteristics of a bhikkhu who tends to the sick, but does not impose
  a penalty on a bhikkhu who cares for the sick but lacks the ideal qualities; at no
  point does the Canon impose a required level of care for the sick. The compilers’
  refusal to mandate a level of care is wise. If there were a case in which the
  bhikkhus did not feel that that level of care was appropriate for their patient,
  they would have only one option: to abandon the patient, so as to incur only a
  dukka˛a and not the potentially higher penalty for not measuring up to the
  mandated care. Thus, instead of protecting the patient, a higher level of
  mandated care would expose the patient to abandonment.) For this reason,
  deciding to withhold or discontinue a particular treatment—while still continuing
  otherwise to care for the patient—would not be grounds for an offense




Beware of the way in which you talk about this subject with others. It is wrong to encourage/counsel suicide.


  c) Describing the advantages of dying. This, the third type of act covered by this
  rule, can include berating a sick person (“Why do you keep hanging on to life
  like this? Don’t you realize what a burden you are to others?”) or simply telling a
  person of the miseries of life or the bliss of dying and going to heaven in such a
  way that he/she might feel inspired to commit suicide or simply pine away to
  death. The Vinita-vatthu also includes under this type of act any statements that
  a nurse might make out of compassion to shorten the miseries of an illness by
  encouraging a patient to let go of life so as not to dawdle in the face of death.
  Thus, the Commentary notes, a bhikkhu talking to a dying patient should be 
  very circumspect in how he chooses his words, focusing not on how to speed up
  the dying process but on how to inspire the patient with the following thoughts:
  “The attainment of the paths and fruitions is not out of the ordinary for a
  virtuous person. So, having formed no attachment for such things as your
  dwelling, and establishing mindfulness in the Buddha, Dhamma, Saºgha, or the
  body, you should be heedful in your attention.” The Vinita-vatthu to Pr 4
  contains a number of stories in which bhikkhus comfort a dying bhikkhu by
  asking him to reflect on what he has attained through the practice, which was
  apparently a common way of encouraging a dying bhikkhu to focus his
  thoughts on the best object possible. The suttas also contain advice on how to
  encourage patients facing death. See, for example, MN 143, SN 36.7, and AN 6.16.
  In all of these cases, the advice is aimed not at precipitating death but at inspiring
  calm and insight.
  
  The Vibhanga notes that a statement describing the advantages of dying
  would fulfill the factor of effort regardless of whether delivered by gesture, by
  voice, by writing, or by means of a messenger. The same holds true for any
  statements under the next type of act.
  
  d) Inciting a person to die, the fourth type of act, covers:
  —Recommending suicide. This includes not only telling a person to commit
  suicide but also giving advice—whether requested or not—on the best ways to
  commit the act.


There's a paragraph on page 85 which may answer your question directly:


  The Commentary extrapolates from this case to apply the dukkata to all
  attempts at suicide, including even the decision not to take food when motivated
  by a desire to die. However, it then runs into the question of how far this penalty
  applies to a bhikkhu who is ill. Its verdict: As long as medicine and attendants are
  available to him, the penalty would still apply. But then it lists two cases where
  the penalty would not apply: (a) A bhikkhu is suffering from a long and serious
  illness, and the attendant bhikkhus are fed up with caring for him, thinking,
  “When will we be free of this sick one?” If the bhikkhu reflects that, even with
  medical care, his body won’t last and that the bhikkhus are being put to
  difficulties, he incurs no penalty in refusing food and medicine. (b) A bhikkhu—
  reflecting that his illness is harsh, the forces of life are running out, and yet the
  noble attainments appear to be within his reach—may refuse food and medicine
  without penalty.
  
  The Commentary’s deliberations here show how difficult it is to legislate in
  this area, and there are reasons to question the way it applies the Great
  Standards here. 


And page 86,


  As for ways of attempting suicide that do not endanger others, it seems
  better to follow the Buddha’s wisdom in not legislating about this issue at all, and
  to treat it as a matter of Dhamma rather than Vinaya. In other words, one
  should keep in mind his comment in SN 35.87 that the only blameless death is an
  arahant’s. If, lacking that attainment, one chooses to refuse food when ill to
  speed up one’s death, one should be heedful of the risks that death and rebirth
  can involve.


You might like to read those several pages from the Vinaya commentary in their entirety (instead of only the quotes above).

Someone also wrote a commantary on the commentary, here: Vinaya Parajika 3 do not kill – accesstoinsight detailed commentary