Jacinda Ardern has spoken about the turmoil her 85-year-old grandfather experienced last night after Waikato Hospital tried to discharge him at 11.30pm.

The Labour leader shared the story at a Grey Power meeting in Nelson today while speaking about mental health and the health system.

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"Do you know what brought this home to me? My grandfather," Ms Ardern said this morning.

"My grandfather was in hospital yesterday in Waikato. At 11.30 at night they tried to discharge him.

"He lives an hour away from the hospital and he's 85-years-old."

Her comments came after Waikato Hospital wrote on Facebook yesterday: "Today our Emergency Department at Waikato Hospital is in overload and Waikato Hospital is full.

"Because of this situation and for the safety of our patients we have to reschedule patients for elective surgery that are not cancer or emergency type surgeries."

Ms Ardern said she didn't "blame the people working in the system they are doing a fabulous job".

"But Waikato hospital is full. That is not good enough.

"That is what this election is about, turning that around," she said.