It achieved that rating last year, and Coeliac New Zealand general manager Dana Alexander said it was unbelievable other hospitals and DHBs had not followed suit.
This week is Coeliac Awareness Week, and CNZ is using the occasion to raise awareness of the importance of providing all diners with gluten-free options, especially in hospitals.
"Our members tell us that when they are in a hospital environment they feel at their lowest and their most vulnerable,'' Ms Alexander said.
"Mercy could see that a number of their patients had specific dietary requirements, as well as coeliac disease and gluten intolerance, and it was increasing.''
"We are delighted Mercy has been at the forefront of this.''
Mercy dietitian Victoria Wood said achieving coeliac safe status had been hard work, but it was an important programme for the wellbeing of patients.
"It can be really debilitating for coeliac patients to eat gluten.
"When you come to hospital you are worried about a whole range of things, and food is one thing we can help with, by offering that reassurance that their food is safe.''
Meeting the accreditation requirements included creating a gluten-free storeroom and prep area, and ensuring there could be no cross-contamination of foodstuffs.
"We had to identify anywhere where there was a potential for cross-contamination and eliminate that,' Ms Wood said.
"We have a chef, Rachel Bond, who we call our gluten-free champion ... who makes sure things are done as they should be and all staff do the online training course through Coeliac NZ.''
Mercy treated several patients with allergy issues and about 10% of them were coeliac, Ms Wood said.
Ms Alexander said Mercy had achieved its accreditation as part of CNZ's "Dining Out'' programme, an initiative aimed at the hospitality sector but open to all food providers.
Southern District Health Board contracts all its food services through Medirest, part of the Compass Group.
Board professional lead dietetics Ruth Thomson said its menu included more than 40 modified or therapeutic diet requirements.
"Gluten-free diets can be catered for by Medirest, with patients receiving a gluten free menu to select from.''
