A coroner has ruled the death of Heather Bills, who died under suspicious circumstances in an Auckland hospital from a massive insulin overdose, was no accident.

Chief Coroner Judge Deborah Marshall released her findings into the 64-year-old's death today, following a lengthy inquest in September.

She found the cause of death was a "non-accidental overdose of insulin".

Bills died at Middlemore Hospital on January 2, 2013, six weeks after she was badly burned in a fire at her Orakei home.

It was later discovered that she suffered a suspicious and massive hypoglycaemia-related cerebral injury.

Her death was due to an overdose of insulin being "introduced to her body from the outside".

Bills was rescued from a devastating and deliberately lit fire at her Auckland home. (Photo / Supplied)

Police suspected three medical workers of administering the fatal dose to Bills on the night of December 26-27, 2012.

Bills was not diabetic and had not been prescribed insulin at the time of her death.

To date, no one has been charged in relation to Bills' death.

Detective Senior Sergeant Ross Ellwood, the officer in charge of the case, told the Heraldtoday that he could not comment specifically on the findings.

"Police will be reviewing the Coroner's findings and our own investigation in relation to this matter," he said.

"This is expected to take some time," he said.

"We are not in a position to say anything further at this time."

Detective Senior Sergeant Ross Ellwood has said he believes Bills was injected. (Photo / Michael Craig)

However, during the inquest Ellwood expressed his views on the case and said Bills' death was the first and only one of its kind in New Zealand.

"I have my own view as to whether [Bills] was injected or not, but my view is not important, it's what I can prove in court," he said.

"I think she was injected. We're looking at someone working in a hospital, potentially causing the death of a patient, and we can't have that."

Chief Coroner Judge Deborah Marshall released her findings today. (Photo / Michael Craig)

Judge Marshall ruled that Bills was able to use her hands, supporting a view that "the insulin must have either been handed to her or administered to her".

"She could not get out of bed to source insulin herself," she said.

"It appears from the evidence that opening a vial and preparing an injection would have been beyond her abilities but she may have been able to inject insulin if it was given to her.

"It is not possible from the evidence to say whether the insulin was administered by injection or intravenously."

Judge Marshall reiterated that it was not her role "to establish civil, criminal or disciplinary liability".

"I am satisfied however that Mrs Bills was administered an overdose ... and that the overdose must have been administered by someone who had access to insulin and the secure National Burns Centre.

"The cause of death was a non-accidental overdose of insulin."

Bills had been pulled from the house fire during the evening of November 22, 2012, when neighbours braved the inferno to rescue her from an upstairs room of her home.

The fire was deliberately lit and she suffered burns to 35 per cent of her body.

While in hospital, Bills displayed suicidal thoughts and offered nurses cash to help her die, the inquest heard.

Michelle Maher (right), Heather Bills' daughter, wanted the inquest to answer questions about her mum's death. (Photo / Michael Craig)

She was then treated at the burns centre and intensive care (ICU) as her condition improved at Middlemore.

But Bills' health rapidly deteriorated on the night of December 26-27, confusing doctors who were "inattentionally blind" to the insulin killing her.

Michelle Maher, Bills' daughter, said at the inquest that her mum had suffered a long and difficult mental illness, and wanted answers about her mum's death.

"Her low blood sugar test results were missed by the medical team on two separate occasions before finally being noticed over five hours from onset of symptoms and three hours after the alarm was first raised by nursing staff.

"I sat bedside as my mum trembled, groaned and gasped to her death over three traumatic days," she said.

She said her mum did not deserve to die in hospital in the way she did and her family deserve the right to know the causes and circumstances surrounding her death.