Terminally ill patients in WA will be allowed to die under a voluntary assisted system due to be in place by 2021.

It follows the state Parliament’s decision late on Thursday night to make voluntary euthanasia legal.

After months of debate, MPs in the state’s Upper House have voted 24-11 in favour.

It means terminally ill adults who are experiencing intolerable suffering and likely have fewer than six months to live — or one year if they have a neurodegenerative condition — will be able to take a drug to end their lives if approved by two doctors.