Foodstuffs group communications director Antoinette Shalleu said it was inappropriate to discuss the customer's details.
"She had a seizure and staff acted immediately, moving her off the ground. An ambulance was called and there was a nurse on the scene helping the customer.
"The paramedics treated her and then a member of staff drove her home," Ms Shalleu said.
"I think the staff acted immediately to make sure that the lady was taken care of."
New World is the second metro-style store to open in the CBD in recent months. Countdown has also opened a store in Victoria St.
"Overseas trends show that urban shoppers tend to shop daily instead of weekly and purchase smaller amounts each time, while expecting high-quality produce, and natural and prepared foods, said New World Metro owner-operator Harry Chawla in a news release.
He was confident that customers would be "blown away" by the quality of the supermarket, and would come to include a visit to the store as part of their daily routine.
"Whether it's a coffee and muffin for breakfast, a freshly made hot ham roll for lunch, or a gourmet ready-meal for dinner, we'll have what they need at New World Metro.
"It's perfect for people wanting to grab some last-minute groceries for dinner as well," he said.
Foodstuffs Auckland managing director Murray Jordan said inner-city shoppers differed from suburban shoppers.
"Our research shows that over 74 per cent are renters, and half are between the ages of 20 and 29.
"Four years ago there were 84,550 workers in the CBD, and in another four years resident numbers are expected to grow to over 31,000, so it's certainly an important customer base for us.
"In 2003, a survey conducted by the Auckland City Council found that 49 per cent of inner-city residents considered the availability of supermarkets in the area needed improvement, so we've definitely come a long way since then."
- Staff reporter
