New figures show a 1.3% hike in demand for ward beds last year, with more than 13,000 extra admissions - but a drop in the number of beds available of 1.4%.
Complaints about the NHS also rose by 13% in 2012/13, according to the new data, sparking suggestions that patient care has suffered because of the pressure on services.
Theresa Fyffe, director of the Royal College of Nursing in Scotland, said the growing elderly population was among the reasons why more people were being admitted to hospital and that many of the patients had complex conditions.
Ms Fyffe said: "What the figures show is we need to look at the whole system of how we provide care to make sure we have the resources and staff both within our hospitals and out in the community to safely care for the increasing number of patients needing care."
The Herald is campaigning for a review of capacity in Scottish hospitals and community care services amid concerns the NHS is struggling to cope with the growing number of elderly patients.
A raft of data about demand for hospital services was released by the statistics arm of NHS Scotland yesterday.
It revealed the number of emergency hospital admissions has increased by 13.8% in a decade, the average number of hospital beds available has fallen by 8.4% in the same timeframe, and the average length of a spell in hospital has dropped by one day since 2006-07 to 4.7 days.
A total of 1,005,595 hospital admissions were recorded in the financial year ending March 2013, up from 992,536 the previous year.
Dr Neil Dewhurst, president of the Royal College of Physicians of Edinburgh, said: "On the surface it is encouraging that patient throughput has increased and that the average length of patient stay has reduced. However, over the last few years the number of medical beds has continued to decrease while bed occupancy levels have continued to rise.
"Bed occupancy has now reached the potentially worrying level of 85% nationally. It is generally accepted that this is the maximum level at which hospitals can operate safely and that occupancy above 85% can cause increased risks and critical problems for patient care."
Complaints about all NHS services reached 9161 in 2012/13 compared to 8117 in 2011/12. Issues about treatment or staff were the most common causes of concern.
Rhoda Grant, Scottish Labour's wellbeing spokeswoman, said: "This is a steep increase in complaints and sadly reflects the growing issues within the NHS that the SNP's culture of cuts has caused."
Health Secretary Alex Neil said: "Scotland's NHS is constantly evolving to ensure it meets the demands of our changing population - not least the vast increase in numbers of people living longer lives. No-one wants to stay in hospital for longer than they need to and we want to ensure that patients are treated quickly and in the location that best suits their needs. That is why over 81% of planned procedures are now carried out as same day surgery, an increase of 10% since 2006/07."
He praised the health service for looking after most of patients well, but underlined the need for complaints to be taken seriously.