Lack of access to pain relief for dying patients is a "public health emergency", say experts.
Figures suggest almost 18 million people - mainly in developing countries - died in unnecessary pain in 2012.
In Ethiopia, there are reports of cancer patients throwing themselves in front of trucks to escape pain.
The Worldwide Palliative Care Alliance says part of the problem is the refusal of governments to give patients access to painkillers such as morphine.
It says restrictions are in place because of exaggerated fears about the risk of addiction.
Last month, health officials from almost 200 countries met at the UN and pledged to make palliative care a higher priority.
This is the first time the specialty has been recognised in this way and championed by the World Health Organization (WHO).
Nestled in a banana plantation in a tiny village in Wakiso district in central Uganda, Betty Naiga, 48, lies on a thin mattress on the floor of her small yellow hut.
She was diagnosed with breast cancer two years ago.
She couldn't afford treatment and the tumour grew to the size of a football.
"The pain was too much before," she said.
"I would not sleep. I would not do anything. It was excruciating. I had given up on life. I wished I was dead."
Betty lay in agony for a year, feeling lost and abandoned by her family. Until she was found by a community volunteer called Allen.
Allen is one of hundreds of volunteers trained by the country's leading palliative care provider, Hospice Africa Uganda, to go out and find people like Betty suffering in silence.
After the hospice got involved with her care, Betty was given access to free chemotherapy and the desperately needed powerful painkiller morphine.
"My life has changed enormously since getting treatment. The medicines help ease my suffering," she said.
Uganda is leading the way in Africa in terms of palliative care. The country makes its own oral morphine using a simple and inexpensive mix of morphine powder and water.
But most other developing countries have very limited supplies.
Some countries, such as Afghanistan and Libya, provide no palliative care, including pain relief.
In Pakistan, more than 350,000 people needed this type of care in 2012, but only around 300 people received any, according to figures seen by the BBC. There are only two palliative care services in the entire country according to the WPCA.
The single service in Mozambique served 153 out of the 100,000 people who needed palliative care in 2012, and in Morocco, 153 people out of 80,000 accessed the country's only service.
At the other extreme are the countries that provide the best access to palliative care. Austria comes out on top providing one palliative care service for every 160 people who need it.
In the UK 97% of people who needed palliative care in 2012 received it.
Morphine is cheap. It's made from raw opium found in the poppy fields of Afghanistan.
It is an internationally controlled drug which means countries have to order their yearly supply from the International Narcotics Control Board.
But many countries are simply not ordering enough.
Dr Stephen Connor, from the WPCA, says there are a number of reasons why this is happening, including exaggerated fears about illicit use and patients becoming addicted to the drug.
"[Governments] are suffering mostly from ignorance, they don't know what palliative care is and that it's possible to relieve suffering," he said.
"Police are trained that any psychoactive substance is a drug of abuse. They don't understand when you have pain and take a reliever, you don't get high. You get pain relief."
Attitudes among doctors also need to change, he said. In most developing countries, medics don't get any palliative care training, including in pain relief.
Many are scared of giving the drug either because of fears about addiction or that the drugs are so powerful they could kill their patients.
He said the key thing that needed to change was attitude.
"You can change laws and regulations and policy, but if you don't change attitudes nothing changes.
"If you are a doctor and you're trained to provide care in a certain way you'll keep doing that."
But there are concerns that while people living in developing countries have very limited access to these drugs, powerful painkillers are being over-used in some higher-income countries.
"Prescription drug abuse is now becoming a major cause of death in the United States," says Dr Lochan Naidoo, president of the International Narcotics Control Board. But he said there needs to be a balanced approach.
"As much as we are warning against the negative consequences (of overdose and addiction), at the same time we don't want to reduce availability in countries that really need it."
But the WPCA said that message was not getting through and it described the current lack of pain relief in most countries as a "public health emergency" which amounted to "torture".
"We've had reports of cancer patients in Ethiopia for instance, throwing themselves in front of large trucks to end their lives because they haven't been able to get access to pain medication.
"This is an intolerable situation," said Dr Connor.
All getting older
Some 4,000 miles from Kampala, in north London. Sara Ray, 69, is proudly gazing at the wall in her lounge, adorned with photos of her five sons.
"Oh I can't bear the idea of leaving them," she said.
"They're just beautiful. They're my best thing."
Sara is dying of a type of lung cancer called mesothelioma. She is receiving some of the best palliative care in the world.
Sara visits a Marie Curie hospice every week where she has psychological and spiritual support as well as access to pain relief.
She can also use their gym, pool and mini-bar and, she says, talk about dying openly and honestly.
"Talking is huge, just getting it out what's inside really helps," she said.
"I suffer an underlying constant pain which is managed by morphine patches and I suffer moments of breathtaking pain like stabs between the ribs and I manage that I manage with liquid morphine but my palliative care team are very anxious that I don't suffer more pain than is necessary.
"Pain frightens me stupid."
Last month, the WHO passed a resolution where governments from all 194 member states pledged to make palliative care a higher priority within their health systems.
Dr Edward Kelly, from WHO, says as the global population ages, access to these services are becoming ever more crucial.
"We're all getting older so the number of diseases like cancer, diabetes, heart disease are becoming more numerous.
"We're also getting better at the healthcare we provide, we keep people alive longer. So the need for better care at the end of life has been growing."
But he admitted major challenges lay ahead: "Many countries are already struggling with the fact they don't have enough money to finance their health systems, so the questions is how will they justify launching new programmes on palliative care for people at the end of life?"
Sara and Betty both passed away within a few weeks of being interviewed by BBC News.
They were given medical and psychological support at the end of their lives.
Something, they said, everyone in their situation deserves.
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