Counting continued on Tuesday and the race remains too close to call.
Mr Turnbull said he remained confident he could get the seats necessary to form a majority government.
His office denied accusations made by opposition leader Bill Shorten that he planned to hold a snap election in the wake of an unclear result.
Australia faces the prospect of a "hung parliament" if neither of the two main parties reaches the 76-seat quota.
With almost 80% of the vote counted, 10 seats remain in doubt, according to the Australian Broadcasting Corp.'s (ABC) analysis.
The ABC has called 68 seats for the ruling Liberal-National coalition, 67 seats for Labor and five for independents and minor parties.
The count was progressing slowly on Tuesday and it is possible the result will not be known for several more days as large numbers of absentee and postal votes are processed.
'Australians were troubled'
Mr Turnbull said there were lessons to be learned from the election.
"It's too early for definitive judgments … it will take time to absorb the learnings from the campaign," he told a press conference in Sydney.
"I want to make it quite clear that as Prime Minister and leader of the Liberal party I take full responsibility for our campaign.
"There is no doubt that there is disillusion with the mainstream parties and we respect that."
Mr Turnbull said again that Labor's repeated claims that the conservative government planned to privatise the public health system, Medicare, were a "grotesque lie".
But he said the fact the "scare campaign" gained traction showed voters believed the government was capable of such actions.
"What we have to recognise is that many Australians were troubled by it, believed it or at least had anxieties raised by it," Mr Turnbull said.
"We have to do more to reaffirm the faith of the Australian people in our commitment to health and to Medicare."
Snap election claim
Mr Shorten held a press conference shortly afterwards where he claimed that Mr Turnbull was planning to hold a snap election.
"There is a very real chance that Malcolm Turnbull is considering calling a snap election in the mistaken belief that this will sort out his own problems," Mr Shorten said.
Mr Shorten dismissed the prime minister's admission of culpability as "a desperate statement from a desperate man trying to keep his job".
Australia has had five prime ministers in the past six years. Despite the poor showing during the coalition's re-election campaign, Mr Turnbull is looking to avoid adding to that tally.
Many analysts predict that Mr Turnbull's coalition will form an administration working closely with crossbenchers to pass legislation.