Up to 60 percent of junior doctors have chosen to work during the latest strike, district health boards say.
Members of the Resident Doctors Association (RDA) are in the fourth day of a five day strike in a row with DHBs over their employment contract.
It is the fifth in a series of strikes since January, and the longest so far.
The main sticking point is that district health boards want hospital chief executives to have the final say over working arrangements, including rosters, rather than the union head office.
The Resident Doctors Association (RDA) union said junior doctors were striking to prevent clawbacks to long-standing terms and conditions of employment.
DHBs said most of the support for the latest strike comes from junior doctors just out of university.
They said 72 percent of registrars - who are more senior doctors training to be specialists - have been working since day one.
DHBs said this shows many share their desire to find a settlement.
"I also want to acknowledge the large number of [junior doctors] who have chosen to work rather than strike this week," DHB spokesman Peter Bramley said.
"Far more people reported for work than expected which has enabled DHBs to maintain a higher level of service.
"Strike action has been entirely unproductive in helping resolve the important issues and has only impacted on the care DHBs provide their communities," he said.
Earlier this week the junior doctors' the RDA said the DHB's figures about the number of staff working were nonsense.
"It's impossible [for there to be] any accurate sort of figure at this stage," union advocate David Monro said.
"Doctors don't clock in or clock out of hospitals and unless somebody's been around counting everybody they're simply not going to know those figures for certain until the pay period rolls around."
The strike ends at 8am on Saturday morning.