Rotorua Hospital is at 80 per cent occupancy with more discharges due during the day.
More than 300 patients at Rotorua and Taupo hospitals were affected with their elective surgeries and outpatient clinic appointments being postponed.
Junior doctor and Rotorua Resident Doctor Association representative Joseph Rea told the Rotorua Daily Post he was disappointed to be going on strike again but the issue of work hours was an important one.
"It is six or so weeks later and here we are having to strike again because no reasonable negotiations could be made. We made good progress last week but it is frustrating having to wait for more negotiations.
"The reason we have gone on strike is such an important issue though and it is nice to know the public supports what we are working towards.
"The patients see what we look like after a 12-day stint and that is what we are trying to fix."
A patient who had her appointment postponed due to the strike said she supported the action, but at the same time was frustrated by her suffering health.
The woman, who wished to remain anonymous, was diagnosed with an overactive thyroid mid-last year.
She said she finally had a specialist appointment booked for next week when she was told it had to be postponed until next month.
"I was absolutely gutted I would have to wait another three-and-a-half weeks. This is my health we're talking about, I can't do anything at the moment."
The woman also suffers from arthritis in her back but cannot continue physiotherapy until her thyroid is treated.
"Safety comes first so I am supportive of the strike but as a patient, it's such bad timing. I've been in hospital six times because of my thyroid but there's not much they can do.
"The times I've been in, I always see the same doctors, they all look tired, one actually yawned on me so I understand they are working crazy hours and something needs to change, but they did pick that career to go into.
"The DHBs need to sort something out that is more reasonable and also keeps our doctors from moving overseas because this can't keep going on."
Locals have been quick to show their support for junior doctors on the Rotorua Daily Post Facebook page.
One person wrote: "Go hard junior drs, you work far too hard, and that's dangerous, common sense is backing you all".
Others said they were backing the strike 100 per cent because the "crazy hours" were dangerous.
In a written statement, Lakes District Health Board chief operating officer Nick Saville-Wood said everything had been "calm and running smoothly" so far.
Mr Saville-Wood said the planning and support of staff including senior doctors, nurses, allied health, hospital managers and support staff was much appreciated and had ensured a "robust contingency plan" to manage emergency services over the three days.
The contingency planning focuses on ensuring the continuing provision of essential emergency services including acute surgery, emergency department care, intensive care, and maternity care.
