A prisoner at Rimutaka who has been on a hunger strike for three weeks is existing solely on electrolytes, sugar pills and water.
The Department of Corrections would not say why the inmate was refusing to eat, citing legal obligations regarding the man's privacy.
In a statement, Rimutaka Prison boss Viv Whelan said the inmate is in segregation where he's being cared for by on-site mental health and medical staff.
"We have comprehensive procedures for caring for people who choose not to eat," Whelan said.
"In line with these procedures, the man is consuming water, electrolytes and glucose tabs and is residing in our Intervention and Support Unit (ISU) where he is receiving care from registered nurses, mental health clinicians and other staff.
"He has been assessed by Forensic Mental Health and will receive further assessments as required. He is also assessed by the prison doctor, who is on site daily, as necessary."
But so far, he's refused a visit from the prison chaplain and kaiwhakamana - Māori elders who have access to the prison.
"We will continue to encourage him to take up this support," Whelan said.
"We appreciate this is a difficult and distressing situation for his whānau and I have taken a number of steps to ensure they can maintain close, ongoing contact with him."
This includes access to daily phonecalls with whānau, fast-tracking visitor application requests and ensuring he is in regular contact with his lawyer.
Family members are also allowed to visit every four days and stay longer, instead of the usual once-a-week visits.
"I have also emailed his family with electronic visitor request forms so they can arrange for family members under the age of 18 to visit the prison. I have progressed these requests to allow these visits to take place as soon as possible.
"To ensure the safety and wellbeing of children, we have to take a number of steps prior to allowing those under the age of 18 to visit a prison. This includes checking that the child's legal guardian has approved the visit and that there are no Court Orders prohibiting contact."
Rimutaka is New Zealand's largest prison, and home to 10 percent of the country's prison population.
It's not the first time hunger strikes have been linked to the Upper Hutt prison. In 2015, transgender and queer activists went on a brief hunger strike to draw attention to trans woman Jade Follett, who was requesting to be moved from Rimutaka - a men's prison - to a women's prison.
Three hours into the strike, she was moved, and Corrections later issued an apology for the two-month delay in transferring her.