The public service watchdog is to urge MSPs to ensure the NHS learns from its mistakes and makes sustainable improvements following years of common complaints.
Recurring themes are failing to prevent falls and bed sores, inadequate nutrition, inadequate care of dementia patients and poor communication with families, according to Scottish Public Services Ombudsman Jim Martin.
He will urge Holyrood's Health and Sport Committee to address the persistent failings as it conducts an inquiry into the regulation of care of older people in acute settings.
In a letter to the committee before his appearance, Mr Martin said: "I see the problems in the cases that people bring to me. In these complaints there are themes and repeated issues across the country.
"Notable among those I can mention are: failing to deal with dementia and cognitive impairment (which can lead to a loss of dignity); issues around communication with families and patients (which can lead to serious disagreement; anger and grief); and failings in what should be simple aspects of care: ensuring adequate nutrition, preventing falls, preventing bed sores.
"There is excellent and outstanding care in the NHS but we do also need to recognise that it does not always reach those standards."
There is a need to learn from mistakes and to ensure improvements are sustainable, amid signs that health workers are reluctant to accept criticism and that any progress is short-lived, he said.
As an example, he cited two reports about care at NHS Lothian, from 2006 and 2012, which raised similar problems and indicated that any improvements made in the intervening years were quickly reversed.
"I have to say that reviewing the two reports six years apart does not make pleasant reading," he said. "I do not intend to highlight NHS Lothian as being a particular problem. I know I could find evidence of failings in all the HIS (scrutiny body Healthcare Improvement Scotland) reports that have been published to date and in reports on complaints about many boards that we have received over a number of years.
"There also does seem, in some areas and on some occasions, to be a reluctance for boards to accept criticisms of their own systems and staff. It can be difficult to work out what the cause for a specific failing is and there can be a complex mix of personalities, systems and resource decisions behind any issue. We will never have an NHS which never fails. However, defensiveness prevents the clear identification of problems and makes it more difficult to implement solutions."