A Queensland private hospital is being sued after a man died following a lethal dose of morphine.

Thirty-three-year-old Michael Calder died at Holy Spirit Northside Private Hospital at Chermside in July 2014 after being admitted for a severe headache.

Deputy coroner John Lock subsequently found both the hospital and the attending physician Dr Rodd Brockett had implemented significant improvements since the incident, and no further changes were necessary.

Mr Calder's partner Andrea Young is launching a $5 million damages claim - includes money for loss of income and services - in the Supreme Court, on behalf of his three sons.

Ms Young's lawyer, Maurice Blackburn's Margaret Brain, said Ms Young needed help to give the boys the opportunities that their father wanted to provide.

“Michael was a hardworking and talented real estate agent, running a high-profile, successful business,” Ms Brain said.

“He was a loving and involved parent and the size of this claim reflects his earning capacity and what he would have provided for his family had he survived the poor treatment.

“Andrea acknowledges and welcomes the changes that the hospital has made since Michael's death and hopes it will ensure that no family will suffer the same ordeal.”