Director of Neurosurgery at The Alfred hospital in Melbourne, Jeffrey Rosenfeld, said Meldrum was in intensive care and remained in a critical condition after suffering extensive injuries while putting up Christmas decorations at his home on Thursday night.
Meldrum broke several ribs, punctured a lung and cracked the back of his head which led to bleeding on his brain.
Dr Rosenfeld said while the entertainment legend had been in a stable condition overnight, he remained in a life-threatening situation.
"We're really concerned for his life, it's a life-and-death matter," Dr Rosenfeld said outside the hospital.
"Here he was perfectly well yesterday and here he is today fighting for his life, we're fighting that battle with him and for him."
Dr Rosenfeld said doctors were doing a brain scan on Meldrum this morning to see how he had responded to surgery overnight.
"We need to wait and see what that scan shows," he said.
"I am encouraged that he's been stable overnight.
"But he's still very seriously ill."
The surgeon said it was too early to predict the chances of a full recovery and the next 24 hours would be critical.
Meldrum's family and friends spent hours at his bedside overnight.
His manager, Mark Klemens, said he was confident Meldrum would recover.
"He's an absolute trooper and whenever he's been down before he gets straight up so I would be hopeful and confident that he'll be back looking down the lens saying: `do yourself a favour'," he told reporters outside the hospital.
"I'm totally optimistic. I've looked after Molly for a long time and he's a great mate so I'm totally optimistic.
"He's a person that endears himself to people and he's iconic, he's a very special man."
Mr Klemens said Meldrum would be humbled by the huge number of messages of support from the public and celebrities including Kylie Minogue and Boy George.
"When he looks back on all this I have absolutely no doubt he'll be humbled and thrilled at the support," he said.
Music promoter and friend Michael Chugg said Meldrum's fall had been heard around the globe.
"I woke up to a lot of texts and emails and messages from all around the world," he told ABC radio in Melbourne.
"I was speaking to Harvey Goldsmith in London 10 minutes ago and they're just mortified, you know it's gone round the world, I've had calls from Billy Joel's people in New York this morning, it's just incredible how much Molly's loved worldwide.
"There's a lot of prayers out there.
"He'll be fighting for his life, he's not ready to bow out yet, I can tell you."
Meldrum's name is synonymous with music in Australia.
He has hosted TV show Countdown, regularly appeared on variety show Hey Hey It's Saturday and has interviewed some of the biggest names in the music world.
Meldrum is famous for his trademark stetson hat and was made a Member of the Order of Australia in 1986 for services to the fostering of international relief and to youth.
