Many New Zealanders are not getting free prescriptions they are entitled to and the most vulnerable are likely to be hardest hit when charges rise next year, researchers warn.

Most people pay $3 per medicine at the pharmacy, and after members of a family have paid for 20 prescription items in a year, all of them should be exempt from the charge.

But Pharmac data show 180,000 people pay for prescriptions after becoming exempt, costing them about $2.5 million a year.

A study into prescription use by researchers at Otago University and Wellington's Victoria University, led by Professor Pauline Norris, shows those affected are likely to include the country's most vulnerable people.


Using anonymous data from community pharmacy computers, researchers identified individuals who had more than 20 items dispensed in a year and found most were from socio-economically deprived areas.

A total of 40 per cent of patients still paid the prescription fee for 90 per cent of the medicines they received, despite being exempt.

Standard charges for prescription medicines are due to rise from $3 to $5 in January. Professor Norris said the exemption meant families should not be required to pay more than $100 a year after the increase comes in. But many people didn't know about the Prescription Subsidy Card needed to get the exemption, or that they had to use one main pharmacy and give receipts from others.