Pharmac says new blood glucose meters now being used by 100,000 people with diabetes are accurate.
The drug-buying agency said last year it is switching from three or four suppliers to a sole supplier, Pharmaco, and its CareSens range.
Some diabetics have complained readings on the new meters differ from those on their old meters, are variable, and have caused problems.
But Pharmac's chief executive, Steffan Crausaz says the CareSens meters meet international standards for accuracy.
He says 300 meters were returned but no incorrect readings were found on those that were tested further.
He says support will continue to be available for those using the new meters.
Meters inaccurate - mother
A woman whose son has type 1 diabetes says Pharmac is wrong in insisting the new meters are accurate.
Helen Lockely, of New Plymouth, says that's not her experience of the new meter.
"People are now having symptoms of hypoglycemia at around five or six - which is in the normal range. Before, people weren't getting hypoglycemia symptoms until four on their old meters - which is where it's supposed to be."
The Diabetes New Zealand patient group says it's received more positive than negative feedback about the new meters but anyone with concerns should seek help.