Frontline clinicians have confirmed NHS Greater Glasgow and Clyde's hospitals have been struggling this week with the kind of pressures usually experienced in winter.
One doctor said there was a "major problem" with capacity, with patients backing up in accident and emergency departments because the wards were full.
Ronald Smith, a patient admitted to the Western Infirmary after collapsing at home on Monday, said he spent more than seven hours in A&E and at times there were nine patients lying on trolleys in the corridors of the emergency department.
Details of the situation have emerged after the Scottish Government announced it was making progress on A&E waiting times, with the proportion of patients treated within four hours rising to 94 per cent.
However, Dr Jason Long, chairman of the college of emergency medicine in Scotland and an A&E doctor in Glasgow, said the situation showed core NHS capacity had to be examined.
He said the college agreed better systems to help prevent hospital admissions and ensure swift discharge were important, but added: "Until that is totally working and bedded in then we have to have enough physical capacity to ensure an emergency department is safe. An emergency department is not safe if there are multiple people on trolleys.
"It is not just affecting the patients waiting six to eight hours and beyond, it affects all the other patients in the department."
The Herald's campaign NHS: Time For Action is calling for a review of capacity in the NHS and social care to ensure services can cope with the growing elderly population.
Mr Smith, 76, arrived at the Western Infirmary at 3pm on Monday and was still lying on a trolley in A&E at 10pm. He described "as many as nine people lying on trolleys awaiting admission". He said one man with a head injury tried to get off to take himself to the toilet after seeking help and not getting it.
Mr Smith's wife, a retired nurse who did not wish to be named, said: "The doctors and nurses were apologising ... I spoke to the senior charge nurse about the problems and he said he had been complaining about it for two years."
She added: "The other patients there had a variety of problems and none looked as though they had brought it on themselves. The hospital obviously was not coping because of the lack of beds."
The health board said: "We have an ageing population with increasingly complex healthcare needs. As a consequence, we are experiencing year-on-year increases in the number of patients admitted to our hospitals as an emergency.
"NHS Greater Glasgow and Clyde is also experiencing pressure on our acute bed availability due to large numbers of patients waiting to be discharged to other more appropriate care settings. Therefore, at times of peak demand on our emergency departments, regrettably some patients can face delays in admission."
The board said it was taking action, with an extra £3.9 million being spent to help move patients through A&Es smoothly. It added: "Any lengthy wait in A&E before admission is not ideal for our patients and we apologise for this.
"However, it is important to stress all patients are assessed by an appropriate clinician when they first arrive at A&E, receive the necessary diagnostic tests, are actively started on treatment where appropriate and continue to be monitored by clinical staff pending admission to a ward."