Susie Williamson, 36, was warned she would have to remain in A&E "indefinitely" after spending hours on a trolley without food, water, blankets or a pillow.
She claimed a doctor told her there were "no beds available anywhere in Glasgow" in the early hours of Thursday, May 29.
NHS Greater Glasgow and Clyde chief executive, Robert Calderwood, was forced to apologise after 37 operations were cancelled following an "unprecedented" surge in demand on Monday, June 2.
Many people were transferred to care homes as admissions rose by 25% across the city.
Claims have been made by a patients' group that "this was not an isolated incident", after Mrs Williamson told of her ordeal.
The 36-year-old, who works for a national charity, was rushed to the Victoria Infirmary with chest pains shortly after 2am on May 29.
She said: "The doctor told me there were no beds available anywhere in Glasgow and that I'd need to stay in A&E indefinitely.
"At around 6am, a nurse came and suggested I try to get some sleep. I explained that as I have some problems with back pain and cramp in my legs due to a long-term health condition, I was finding the trolley uncomfortable and so preferred to sit in the chair in the bay, meaning sleep wasn't really possible.
"I also explained I was cold - she sympathised but said there were no pillows or blankets available, but she'd see what she could do. Around half an hour later, she brought me a blanket.
"I was told then that there were still no beds available and they couldn't tell me how long I'd have to stay in A&E."
Mrs Williamson was due to take medication at 7am for neurosarcoidosis, a chronicdisorder which affects major organs.
Realising she didn't have it with her, she signed herself out and took a taxi home to Rutherglen. She said: "There was no water or food available. I was exhausted, cold and hungry. I felt I had to do this. I've heard nothing since."
Chairwoman of Scotland Patients Association Margaret Watt described Mrs Williamson's treatment as "absolutely shocking".
She said: "This shows that the situation on Monday, June 2 was not an isolated incident. We are in 2014 and it's high time this was sorted out. People must be treated with respect and dignity."
Mrs Williamson added: "All the staff were efficient and helpful, and in no way do I think this situation was their fault."
An NHS spokeswoman issued apologised to Mrs Williamson.
She added: "We are sorry that this patient was unhappy with the care she received.
"She was assessed within 10 minutes of arrival at A&E and our records show that she was in the department for less than 4 and a half hours before deciding to leave prior to any decision being taken as to whether she needed admission or not.
"Our A&E departments were busy on Thursday 29th May however any patients requiring a bed were admitted."