Patients being given the wrong prescription occurs "a lot", Dr David Galler from the Health Quality and Safety Commission says.

However it is hoped a new National Medication Chart will ensure there are no future errors with the prescription process.

Dr Galler's comments come following the tragic death of Shirley Curtis, who died after being mistakenly given 10-times the prescribed dose of metaprolol, a beta blocker medicine by a nurse at North Shore Hospital.

The nurse, who has a previous unblemished record, has been stood down and the Waitemata District Health Board is investigating the error.

Dr Galler said there is a problem with the way prescriptions are written in New Zealand.

"We've seen, in fact health systems all around the world, have seen these kind of problems occur," Dr Galler said.

"A ten-times overdose is a decimal point problem. It's actually lack of clarity around the prescription or misinterpretation of the prescription."

Dr Galler said between 20 to 30 per cent of people suffer some degree of harm from medication - although the vast majority of those harms are minor, such as nausea, or a minor rash. Half of those are caused by prescribing or administration errors, he said.

"That happens and it happens a lot. Occasionally you get a really bad one like this. There are ways of avoiding that through the design of forms and also through other ways of prescribing, like electronic prescribing."

Dr Galler said the new National Medication Chart which is being rolled out at DHBs across the country will make mistakes far less common.

The Bay of Plenty, Lakes, MidCentral, Nelson Marlborough and West Coast DHBS have introduced the chart, while three others will do so by the end of May.

"The National Medication Chart has a formatted decimal point in it so it is very clear about where that decimal point ought to be," he said.

"It is quite carefully put together to ensure the prescribing information is absolutely clear.

"Waitemata are due to adopt it by the end of the year - they may reconsider that and do it a bit faster.

"My own district health board in Counties has been using a preformatted prescription chart for 18 months prior to the introduction to the new chart ... and we haven't had any incidents of this kind of thing happening in that time - we've certainly have had them before.

In the future the system will become electronic, Mr Galler said, reducing errors even further.

A date has not been set for the system to become automated, but pilot systems are currently being trialled.

"Those pilots will eventually lead to a nationwide roll out. That has the potential for huge safety benefits."

Dr Galler said while future tragedies may be averted, he acknowledged the system had failed the Curtis family.

"For everyone involved it is a life-changing event," he said.

While he said we must wait for the investigation to be completed, we should resist the temptation to hang the staff involved "out to dry".

"The reality is we are not working with systems that are as safe as they could be. That is where our focus needs to lie."