Almost 10,000 people were accidentally harmed by the hospitals trying to help them last year.
The ACC has forked out close to $675 million in the past decade for patients injured after botched medical treatments, misdiagnosis, post-surgery infections and reactions to medications.
The ACC released a report on treatment injuries, cases where patients were unintentionally harmed during medical treatment, in the 2015/2016 financial year today.
It found that 8881 treatment injury claims were accepted. With 5002 coming from a public DHB hospital, a further 3879 treatment injuries were sustained in private hospitals, general practice, and other health settings.
The report stated that the number of claims and cost had increased. In the past 10 years, the number of treatment injury claims accepted by ACC has increased by 170%, from 3269 accepted claims.
"The actual and predicted future costs for all treatment injuries last year was $418 million. ACC's predicted liability for the future costs of all treatment injuries to date is $5 billion," the report stated.
ACC chief clinical advisor Dr Peter Robinson said the number of treatment injury claims had grown steadily since ACC cover was expanded in 2005 to all treatment injuries.
"International research suggests 40% to 60% of those could have been avoided or at least the severity minimised. That shows the importance of ACC and the health sector working together on injury prevention initiatives."
The report is part of a sector-wide programme to support improvements in patient safety, reduce patient harm and reduce treatment injuries.
In light of this report ACC is to invest up to $45 million in treatment injury prevention programmes in the next five years.
These include initiatives to reduce infections, pressure injuries and birth brain injuries, as well as practices to ensure safer surgery. Infections and pressure injuries make up the highest number of accepted treatment injury claims to ACC with 1364 recorded last year.
The $45 million investment is also for future initiatives, which ACC will develop alongside the health sector.
ACC chief customer officer Mike Tully said the investment aims to improve patient safety and injury prevention is one of the key functions.
"We are doing this to ensure all of us in the health sector can understand and learn from treatment injuries, so they are less likely to occur in the future."
Treatment injuries claims for each DHB:
Auckland DHB 538
Bay of Plenty DHB 204
Canterbury DHB 414
Capital & Coast DHB 526
Manukau DHB 458
Hawke's Bay DHB 126
Hutt Valley DHB 248
Lakes DHB 103
MidCentral DHB 187
Nelson Marlborough DHB 197
Northland DHB 223
South Canterbury DHB 109
Southern DHB 228
Tairawhiti DHB 68
Taranaki DHB 245
Waikato DHB 571
Wairarapa DHB 86
Waitemata DHB 324
West Coast DHB 28
Whanganui DHB 119
ACC state that a simple comparison between DHBs is not valid as each one has different case mixes, demographics and/or socio-economic conditions among the catchment population. These can influence the risk of treatment injury.