An organ transplant can be the difference between life and death for many people.
For those in need of one, the wait for a call from hospital to say a match is available is an excruciating one.
Sometimes life outruns them before the call comes.
And so a booming black market for human organs has emerged in several countries including India and Pakistan.
Researchers say China is home to the most rampant illegal organ trade in the world and is the number one destination for 'transplant tourism'.
The practice sees desperate people - from countries where waiting lists are longer than their life expectancy or costs are exorbitant - travel overseas to buy an organ and have lifesaving surgery.
But there's a major catch: Researchers say the donor organs are often sourced illegally from prisoners executed for their religious, political or cultural beliefs, who have not consented to any of it.
Many of China's prisoners have testified to having been subjected to medical testing consistent with organ transplant screening but without explanation while behind bars.
"They called these people the living dead. You just haven't died yet, but you're gone," one organ transplant recipient said.
The man, who didn't want to be identified, told PBS News Hour he had end-stage kidney disease 11 years ago until he travelled to China and paid $10,000 for a transplant.
Within one week, he received a new kidney.
He said he would have died before he reached the top of the waiting list for a new kidney in Canada, where he lives with his family.
"I went there dead. I came back alive."
China condemns practice but still happening
In 2005, Chinese officials admitted they harvested organs from prisoners and promised to reform the practice.
In the years that followed, several doctors were arrested for allegedly carrying out illegal organ transplants at private clinics, according to local authorities and state media.
Acting on a tip-off, police in Bazhou city in the northern province of Hebei arrested three doctors as they prepared to remove a kidney from a man, a local Communist Party official and police told AFP in 2011.
In 2013, director of the China Organ Donation Committee, Dr Huang Jiefu, told medical journal The Lancet that more than 90 per cent of transplant organs were still sourced from executed prisoners.
China announced the following year that it would end the harvesting of organs from executed prisoners and move to a voluntary donation-based system.
But according to several reports, the controversial practice is far from abolished, and there is evidence it still continues.
Thousands of mysterious human organs on offer
Recently published research by author Ethan Gutmann, former Canadian politician David Kilgour and lawyer David Matas claims China is performing 60,000 to 100,000 organ transplants a year.
They say this dwarfs the Communist regime's estimates of about 10,000 and that it cannot be explained by China's fledgling program for voluntary organ donors.
"The (Communist Party) says the total number of legal transplants is about 10,000 per year. But we can easily surpass the official Chinese figure just by looking at the two or three biggest hospitals," Matas said.
"That increased discrepancy leads us to conclude that there has been a far larger slaughter of practitioners of Falun Gong for their organs than we had originally estimated."
The investigators claim many of the organs are taken from prisoners of conscience, mainly the persecuted Falun Gong religious minority, but also Uyghurs, Tibetans and "House Christians" who congregate secretly in worshippers' homes.
The damning report accuses the Chinese government of continuing to carry out mass killings of innocent people in order to obtain their organs for transplants.
"We interviewed Falun Gong who got out of prison, got out of China, systematically blood-tested, organ-examined, not for their health - they were being tortured - and only the types of examinations relevant to transplantation," Matas said.
News.com.au last year interviewed about half a dozen Chinese refugees who had been imprisoned in China for their spiritual beliefs. They all reported having been subjected to torture and medical testing while in prison.
Australians 'coming back with livers from prisoners'
Demand for transplants far exceeds supply in China, a country of more than 1.3 billion, which has opened the door to the illegal sale of human organs.
Researchers estimate that as many as 1.5 million victims have had their organs harvested for China's transplant industry.
Patients reportedly pay about $15,000 for an illegal organ transplant operation in China, according to previous state media reports.
In the US, the average hospital charge for a kidney transplant is $150,000.
In Canada and Australia it's free, because the government pays for health care. But wait lists can be long. For some, too long.
According to the Australia & New Zealand Dialysis & Transplant Registry (ANZDATA), at least 55 Australians travelled overseas to receive a kidney transplant between 2006-2015.
The data isn't broken down by countries and doesn't include figures of Australians who have travelled overseas for transplants of organs other than kidneys, such as livers.
"It is possible that these numbers are an underestimate of the true number, since some patients may not return to Australia/New Zealand and hence be reported to ANZDATA as lost to follow-up," ANZDATA's 2016 annual report read.
In December 2013, Professor Jeremy Chapman expressed grave doubts about China's transplant program in the Medical Journal of Australia, stating that "China cannot enter the global community of civil societies while current practice continues in its prisons and hospitals".
Prof Chapman also quoted a physician in Australia who was allegedly told by a patient of Chinese origin: "I cannot come in for dialysis tomorrow. I have to fly tonight because they are shooting my donor tomorrow."
In an open letter published on The Transplantation Society's website, Prof Chapman said the organisation "supports those in China who are agents for change" and is committed to the development of "an ethically based, transparent, deceased organ donor program, which must be free of corruption and financial incentives".
Researcher Ethan Gutmann told news.com.au that transplant tourism needs to stop.
"There needs to be an end to the normalisation of mass murder," he said.
"Israel, Spain and Taiwan have banned it. That took guts. So how about this: No more Australians going to China on the QT, and coming back with a liver taken from a political or religious prisoner?"
Derryn Hinch encouraged to have illegal transplant
Senator Derryn Hinch said he was encouraged to travel to China for an organ transplant after he was told he had only 12 months to live.
"As the months ticked by and there did not seem to be any chance, other than a couple of false alarms, of getting a new liver, I was told by a senior businessman in Melbourne that I could go to Shanghai and for $150,000 get a new liver next week," Hinch told parliament in November last year.
"I presume from that they would almost execute on order. How you could morally extend your life by doing that I cannot believe, but I was also told I could go to India and do the same thing.
"Some well-known people have bought organs for transplant over the years. But I condemn those practices in China."
'In China they make you dead'
Doctors Against Forced Organ Harvesting (DAFOH) performs systematic research into the reports of the state-sanctioned practice in China from prisoners of conscience.
DAFOH Australia spokeswoman Sophia Bryskine said the organisation was "particularly focused on China because, unlike anywhere else in the world, it is the only place where systematic forced organ harvesting continues to occur on a mass, state-sanctioned level".
"There are no formal laws prohibiting the practice," Dr Bryskine said.
"In fact, a '1984 Provision' still remains in place, which allows for executed prisoners to be used as donors - in direct violation of all international guidelines."
Dr Bryskine said a lot of prisoners "don't even go through a legal sitting".
"The Chinese legal system is corrupt," she said. "It has to stop."
Arthur Caplan, leading US ethicist and founding director of the Division of Medical Ethics at NYU, offered his observations on organ harvesting in China.
"In the US or Europe, you have to be dead first in order to be an organ donor. In China, they make you dead," he said.
Chinese Foreign Ministry spokeswoman Hua Chunying said China has "strict laws and regulations on this issue."
"As for the testimony and the published report, I want to say that such stories about forced organ harvesting in China are imaginary and baseless - they don't have any factual foundation," she said at a press conference.
The National Health and Family Planning Commission, which oversees organ donations in China, could not be contacted for comment.
The Dui Hua Foundation, which monitors executions in China, estimates that approximately 2,400 people were put to death in 2013. Official figures on executions remain a state secret.
China: the world's biggest executioner
The Chinese Government has repeatedly refused to reveal how many people it executes each year.
China was named the world's biggest executioner in Amnesty International's Death Sentences and Executions 2015 report.
The human rights group said it was impossible to obtain an exact figure on the number of people China has executed, but it is believed the figure is in the thousands, and is more than all the other countries in the world combined.
China was also named as the world's top executioner in 2014, with Amnesty estimating it was at least 1000 - a conservative figure, and one it believes is much higher.
However the 2016 report did note, there are indications that the number of executions has decreased since the Supreme People's Court began reviewing the implementation of the death penalty in 2007.
According to Amnesty International, "tens of thousands of Falun Gong practitioners have been arbitrarily detained" since the government launched a crackdown on the practice in 1999.