Two people spoken to by Radio New Zealand have reported rises of 35% and 15% in health insurance levies.
The Health Funds Association says it can not comment on individual cases.
But executive director Roger Stiles says medical costs increase faster than inflation and are currently around twice as high.
He says more claims are also being made and medical procedures vary in cost and complexity.
Mr Stiles says the cost can increase faster for some individuals than others and a person's age also plays a part.