Te Kuiti Hospital is at capacity and is turning patients away.
The hospital's 12 beds are all full and any patients that need to be admitted to hospital are being transferred to Waikato Hospital instead.
Waikato District Health Board director of communications Lydia Aydon said the hospital reached capacity one or two times a year and it usually only lasted about 24 hours.
"We are expecting it to be back to normal tomorrow."
The hospital had notified St John Ambulance so that drivers took patients to Waikato Hospital instead of Te Kuiti.
Te Kuiti Hospital's emergency department was still treating patients, but anyone who needed to be admitted would be taken to Hamilton.