Health officials say they are investigating claims a patient admitted to hospital with breathing difficulties was forced to do a 23-mile journey home on foot.
Peter Rees was taken by ambulance to Glangwili's accident and emergency unit in Carmarthen, west Wales, on 31 December because he was struggling to catch his breath.
Doctors diagnosed the 62-year-old with a chest infection.
But the father-of-three has voiced his anger after claiming he was sent on his way at 2am on New Year's Day without being offered any help to get home.
Mr Rees, who said he did not have a wallet on him due to his emergency admission, reportedly walked 12 miles on dark country roads until a passing police car gave him a lift.
"It was dreadful; the most horrible night of my life. I had dark clothing on, I was feeling most unwell and I had to walk on unlit roads on one of the most dangerous nights of the year," the South Wales Evening Post quoted him as saying.
"I was literally clinging on to bramble bushes as I edged along the hedgerow in the face of oncoming traffic. I was shattered, freezing, I felt giddy and I lost my footing more than once."
Mr Rees had been at home in the village of Llanwrda, near Llandeilo, on New Year's Eve when he was hit by a bout of uncontrollable coughing and shortness of breath. He was examined by a paramedic at home, who called for an ambulance to admit him to hospital.
After X-rays, blood tests and an examination Mr Rees was told he could go home.
"They told me I had a chest infection and released me with a course of strong antibiotics. When I said I couldn't believe what was happening, I was accused of being aggressive," he said.
"I was very tired but I didn't raise my voice or swear. I was not aggressive but they said I had to leave. Hospitals are supposed to be caring places.
"It was heartless and no way to treat a man of my age who had just been diagnosed with a chest infection."
He said he walked 10 miles before encountering a police officer who urged him not to walk any further because it was "too dangerous".
It was then two miles later that a police car stopped and took him home where he lives with partner Annie, Mr Rees said.
He has since made an official complaint to Hywel Dda Health Board which runs Glangwili, also known as West Wales General Hospital.
A spokesman for the health board said: "We regret to hear about the situation Mr Rees found himself in on New Year's Day. The board has now received a formal complaint and as the investigation is ongoing, we cannot comment further at this time.
"We'd like to reassure the public that there are a range of transport schemes in place, or being piloted, for patients who require assistance with non-emergency transportation."