Personally I think Hinduism is not against  “Assisted death”! Hindus believe in rebirth/reincarnation. But that is different from Buddhist/Jain Karma Siddhanta which causes in the belief of a certain definite previous birth.  Often even Hindu faith followers  quote Karma Siddhanta as understood by Buddhists/Jains and say that you have to suffer your karma.  There was an inherit assumption that the being (soul) is suffering because of karma performed in previous birth.  And if the being abruptly ends his life then he will take birth again to suffer further!
But in my humble opinion,  this assumption is not correct. Hindus do not apply Karma siddhanta in this context to justify suffering. Hindus position is that no being deserves unnecessary suffering.  Even though we Hindus agree that beings take birth,  we don’t agree that there was definitely a previous birth! It may be or may not be! Which means this very birth may be your first birth!  If we agree that we have rebirth then logically there should be a beginning birth… i.e. You should have taken your first birth at some point! So that first birth could be this birth itself!  That is why our Seers say that you are suffering because of no reason what so ever. Your identification alone makes you suffer – not your “prarabdha karma”… It is “avidya” (not knowing the nature of your true self) which makes you suffer.  “Your true self is not your physical body!  You are different than your body!” is the teaching of our Hindu Seers.
Also Sri Gaudapadacharya in his doctrine of Ajatavada says that the “Absolute is not subject to birth, change and death. The Absolute is aja, the unborn eternal” —  Therefore that which never took birth can not undergo death!We Hindus recognize two levels of suffering:
(1) Suffering at the Physical body level (sthula sarira)
(2) Suffering at the Mental level (Sukshsma and Karana Sarira)The level 1 suffering is what can be considered as “Vehicular suffering”.  The physical body is understood as a vehicle for Atman (soul).

Let us Imagine you are travelling in a car and it got all flat tyres, or it’s engine is broken down. What will you do under those circumstances?!  You will voluntarily leave your vehicle and travel further in a new vehicle.  It is your wilful decision to leave your vehicle.  Perhaps your entire vehicle is not broken down but just one tyre got punctured.  You will change the tyre and continue your journey further.

atmanam rathinam viddhi sariram ratham eva ca
buddhim tu sarathim viddhi manah pragraham eva ca
indriyani hayan ahur visayams tesu gocaran
atmendriya-mano-yuktam bhoktety ahur manisinah

“The individual is the passenger in the car of the material body, and intelligence is the driver. Mind is the driving instrument, and the senses are the horses. The self is thus the enjoyer or sufferer in the association of the mind and senses. So it is understood by great thinkers.”

Our Physical body is like such a vehicle.  It can break down. It breaks down inevitably at some point in future time.  Also it may become unworthy for any further travel. We need not give more importance to the physical body than what is given to a vehicle we own. Therefore it is perfectly OK to give up the body when our body becomes uncooperative.

The decision about the body is always in the hands of the owner (Atman). For example, when someone is suffering from terrible appendicitis pain they get operation done to remove it – to get rid of the pain  We must apply this learning to the entire human body. ..What if the whole body is paining? What should the Atman (owner of the physical body) do?! There is a reason for pain in the body.  Pain is a signal asking the vehicle owner (atman) to do something about it.  The Atman (soul) may decide to take pain killers, but in the end he may have to eventually walk out of the body. It is in this context, when the pain becomes unbearable, I think it is OK the individual to decide for himself. It is his life and his pain.

Instead of allowing the vehicle owner to get out of his broken vehicle, what if we lock the doors and forcedly keep him confined in his vehicle?  How terrible he would feel?! How helpless he would feel?!  Our relatives who may be undergoing terrible suffering from their physical body may be begging us to allow them to get out of their broken vehicle, but we are only inflicting further misery on them by forcedly confining them in their broken vehicle.  By doing so perhaps we are attracting further Karma towards ourselves?!   i.e. we are committing an error in judgement in karma.In Mahabharata we know the story of Dhritarashtra and Gandhari ending their life at the old age.  Those who practise Yoga can voluntarily walk out of their bodies.  Swamy Ramatirdha left his body in a water.  Swamy Vivekananda died quite young in a YogaAsana.   .

So does this mean Hindus permit suicide?!  Absolutely NOT!!As I said there are two levels of suffering. The second level of suffering we recognize is entirely subjective and related to Atman.  Suffering at the mental level, depressions and mental imaginations, losses etc.,  our Hindu scriptures are strictly against ending life for mental reasons they called it “Atmahana”

asuryAnAmatE lOkAH aMdhEna tamasAvRutAH
tAMstE prEtyABi gaccaMti EkEcAtmahanO janAH  – SuklayajurvEda – Easavasya Upanishad Sloka 3
There are worlds called “asurya” full of darkness. Those who kill themselves for selfish reasons ‘atma hana’ go there. Committing suicide for mental level disturbances is strictly forbidden. Because such suffering is only assumed and purely imaginary. Imagine someone assumes that his Employer is going to remove him from job. He might feel depressed, may try to commit suicide. But what if his assumption is totally wrong? what if his assumption is totally wrong?! Therefore there is always time to get clarification. So Hinduism does not permit people to take hasty decisions in the context mental sufferings. Therefore suicide for mental reasons is a big NO.. Also this is one of the reasons Hindus believe in vijigisha sanyasa. You are permitted to renounce your life, give up your profession, change your name, do your own kriyakarma (funeral rites) and become a monk. Such Sanyasa will give relief from the mental suffering. Arjuna wished for this type of Sanyasa in Bhgawad Gita. “SrEyO bhOktuM bhaikShyaM api iha lOke” – Gita 2.5Therefore I strongly believe if the Jiva (soul / atman) want to leave his vehicle because it has broken down and it is unrepairable then it is perfectly all right to allow him to take a decision to let go of his vehicle. Because in reality he is not dying but he is switching the vehicles! It is their body their pain, if they want to go LET THEM GO in peace and wish them Bon Voyage….The duty of a relative is to respect the wish of his relative – Valmiki Ramayana

There are too many instances of great men giving up their body in many scriptures. for Instance in Ramayana,  both Rama and Lakshmana gave up their bodies.

sa gatvaa sarayoo teeram upaspruSya kritaamjalih |
nirguhya sarva strotraaMsi niH SvaasaM na mumEvaca ||
                                                             Valimiki Ramayan – Uttarakanda 106.15
[Lakshmana] Having reached the banks of Sarayu, he performed ablutions, restraining all senses, held his breathe [thus dying to this world and ascending to heaven]

But before Lakshmana decided to give up his life he took permission from Lord Srirama. Though Srirama initially did not agree but Brahmashi Vashistha ji and other great sages tell Sriramji to allow Lakshmana to pass away! 

Vashitaji said these words to Rama:

“Leave him (Lakshmana). Time (Death) is in deed too powerful, do not give up your promise, for it being given up, righteousness will perish” Valimiki Ramayan – Uttarakanda 106.9

So here we have an example from our Srimad Ramayan where The brother Rama (relative) is allowing his relative to follow his right to choose willing death! So our scriptures can’t be more explicit than this!

Rama was distraught to let go Lakshmana, but yet he respected Lakshmana’s wish to die and let him die!
Love,
Madhava TurumellaP.S: Founder of “Hinduism Today” Satguru Sivaya Subramuniyaswami passed away in the year 2001. He refused treatment. 

A spokesperson for the ashram said the Hindu master discovered on October 9 that he had advanced intestinal cancer. Three medical teams of radiologists and oncologists in Hawaii, Washington State and California all concurred that even the most aggressive treatment regimens would not prove effective, and estimated he had just a few months to live. Consequently, Subramuniyaswami declined any treatment beyond palliative measures, and made the decision to follow the Indian yogic practice, called Prayopavesa in Sanskrit scripture, to abstain from nourishment and take water only from that day on. He died on the 32nd day of his self-declared fast, passing on quietly at 11:54 pm on November 12, 2001, surrounded by his 23 monastics.

Please see I am giving below his view:

satguru