Robert Wilson was transferred to the Memorial Hospital with a broken arm
A medical expert believed a 74-year-old man may have left a Hampshire hospital alive if he not been "started on a high dose of diamorphine", an inquest heard.
Robert Wilson was admitted to Gosport War Memorial Hospital in 1998 after breaking his arm but he also had a serious liver condition, jurors heard.
Prof Richard Baker's assertion came after he had seen Mr Wilson's records.
Inquests are being held at Portsmouth Coroner's Court into the deaths of 10 patients more than 10 years ago.
When Mr Wilson was admitted on 14 October 1998 he was administered morphine tablets every four hours.
This dosage continued the following day, the hearing heard.
But on the evening of 16 October he was given diamorphine through a syringe driver and that higher dosage continued until the day of Mr Wilson's death on 18 October.
On the death certificate the cause of death was given as heart failure/liver failure.
The coroner read a statement from Prof Baker, of the University of Leicester's department of health and sciences which said: "The initiation of the diamorphine was inappropriate and the starting dose too high.
"Mr Wilson might have left the hospital alive if he had not been started on diamorphine."
Prof Baker also said one alternative would have been to stop the medication to see if he improved, the hearing heard.
Hampshire Police carried out a series of investigations into the treatment of patients at the hospital in the late 1990s, but no prosecutions have been brought.
The inquests, expected to last six weeks, are being held into the deaths of Arthur Cunningham, 79, Elsie Devine, 88, Sheila Gregory, 91, Ruby Lake, 84, Elsie Lavender, 83, Geoffrey Packman, 67, Leslie Pittock, 83, Helena Service, 99, Enid Spurgin, 92, and Robert Wilson, 74.
The inquest was adjourned until Wednesday.