Drug-buying agency Pharmac says its work has saved district health boards more than $5 billion over the past 12 years.
In its latest annual report, the agency also says it has expanded access to medicines while staying within budget.
Pharmac says the figure of $5 billion in savings is based on 1999 prices, actual prescribing, and comparing what would have happened if it had not taken action through negotiations and other initiatives.
The agency is expanding its role to include management of hospital medicines, saying an agreement with drug firm Pfizer over injections for pain following surgery is saving DHBs $1 million over five years.
Pharmac says it funded a record 41.1 million prescriptions for 3.3 million New Zealanders last year within its $777 million budget.
It says without its efforts, savings would have to come from other areas of health spending.