Margaret Hall, 78, was "roaring with pain" during her final hours at the Bupa-run Eastbank Care Home in Shettleston, her daughter has said.
It is the latest scandal to hit the private care home chain after police launched an inquiry last week into the deaths of four residents at a Bupa home in Edinburgh, amid reports that residents were left starving and deprived of water.
Mrs Hall's family have lodged five complaints about her care at the Glasgow premises, where the mother-of-three died on July 5 this year.
Her daughter, Elizabeth Peebles, 53, said: "The day she died I found her sitting right under the TV in a packed lounge. I could instantly see the deathly colour of her."
Mrs Hall was taken off her medication by staff four days before her death, but the family has complained no pain relief was provided to ease her suffering.
Mrs Hall's husband, Eric, 75, added: "End-of-life care should have been in place as soon as she came off her medication. It was appalling to watch."
In a letter to the family, Glasgow area manager Darren Kelly acknowledged shortcomings in the pensioner's care.
Bupa said that staff training had been stepped up following the incident.