A series of "appalling" examples of poor care, where patients are said to have been neglected, left in pain and without food and water, are being highlighted by campaigners.
The Patients Association said its dossier of 13 cases should act as a wake-up call to the NHS across the UK.
Too many patients were still being let down, although there was much to be proud of in the NHS, it said.
Trusts said "decisive action" was needed when poor care was identified.
The report is the fourth time the Patients Association, a charity, has publicised poor care in this way.
It said the underlying causes - bad communication, lack of help going to the toilet, access to pain relief and nutrition - had remained the same throughout.
The charity said the stories it had highlighted also reflected what many of 8,000 callers had reported to their helpline last year.
Among the cases documented is one involving a dementia patient who went missing from a hospital and was found drowned in a nearby river.
In other examples, a 91-year-old woman was left sitting naked on an incontinence pad, while a man was left to drink from a mug used to hold toothbrushes.
A number of the patient stories involved people who had been left in soiled sheets and there were examples of patients having a "do not resuscitate order" placed on them without proper discussion with their families.
Patients Association chief executive Katherine Murphy said: "The sad conclusion of this report is that still too many patients are being shockingly let down by the NHS every day.
"These appalling and tragic cases serve to highlight the devastating consequences when poor practice is left unchallenged and unchanged.
"Behind each one are many more unheard voices. Whilst there is a lot to be proud of about the NHS, including the overwhelming majority of staff who are skilled and hard-working, these cases are a tragic wake-up call."
Publication of the case studies, which predominantly focused on hospital care, comes ahead of the release of a report by the Care Quality Commission on Friday into how many NHS trusts are failing essential standards.
The CQC said it had been working with the Patients Association to tap into the problems that were being reported to them.
A spokesman for the regulator said: "We all need to make sure that experiences like this are listened to and acted on so that people's care improves."
Mike Farrar, chief executive of the NHS Confederation, which represents trusts, said: "The stories in this report are shocking and deeply distressing. There is no-one working in the NHS who will not feel saddened by what these patients and their carers have gone through.
"Our purpose is to care and we need to take responsibility for the issues that really matter to the people who use our services. We should never excuse poor standards of care and we need to take bold and decisive action when we see it happening."
His comments were echoed by Royal College of Nursing general secretary Peter Carter.
He said: "This is completely unacceptable and every healthcare professional must act promptly to raise concerns if staffing levels or other pressures get in the way of delivering good patient care."