"Something went amiss on the summit push after C2 (Camp 2). In hospital … surprisingly mum is here … which is good to get medical advice.
"Body wrecked with liver problems, no phone and vision damage. Piecing (together) what happened. Rest."
Before his climb, Mr Lee had indicated on his blog he was attempting to complete it without using oxygen tanks.
"I have put a lot of pressure onto myself," he wrote in the blog post. "I am running out of (money) to keep chasing this dream.
When asked on Facebook before his climb about not using oxygen, Mr Lee replied that if he was climbing with oxygen "I might as well chop 50 per cent of the mountain height off".
It was Mr Lee's fourth attempt to climb Mt Everest, the world's highest mountain at 8848m, after failed attempts in 2015, 2017 and 2018.
During the expedition, Mr Lee had tweeted he'd had a "rough night" from a persistent chest infection at Camp 1, at about 6000m.
By 7000m, Mr Lee's health was "not really good", according to the part-owner of the expedition company the Aussie climbed with.
"Our team guide suggest him to (go) back from the North Col but he didn't accept and he continued to 7600 metres," Tashi Sherpa told the ABC.
Another mountaineer told the ABC that Mr Lee had "so much trouble with acclimatisation" and was "coughing continuously".
Mr Lee's dramatic rescue has come amid a horror season on Mt Everest, which has been marred by reports of human traffic jams as a record number of climbers scramble for the top.
Eleven climbers have died on Mt Everest this year, including nine in Nepal — the worst death toll since 2015.
Photographs taken this month by adventure filmmaker Elia Saikaly show chaotic scenes in the mountain's "death zone", near the summit, as massive influxes of climbers create long queues.
"I cannot believe what I saw up there," Saikaly wrote of the scene.
"Death. Carnage. Chaos. Line-ups. Dead bodies on the route and in tents at camp 4. People who I tried to turn back who ended up dying. People being dragged down. Walking over bodies."
Tourism officials issued more permits to climbers than ever before this year, which seasoned mountaineers believe has contributed to massive crowds on the way to the summit.
This season has also seen a smaller window of optimal weather than usual, which has limited the amount of time people have to climb.
Amateur climbers have also been blamed for faltering on their way up the mountain, holding up others and leaving them exposed for longer than ideal to the high altitude and extreme conditions.
"There are inexperienced climbers who don't know the basics of putting their gear on," the youngest Australian to scale Mt Everest, Alyssa Azar, told the Today show this week.
"That zone is dangerous already without those sort of accidents happening. When you get to Camp 4 and you are officially in that death zone, you really have sort of a 24-hour time limit.
"So if you haven't reached the summit within 12 hours, you have to turn around because you are going to run out of oxygen.
"Often people die up there because of exhaustion and the lack of oxygen. So it is dangerous already."
There have been calls on Nepal to cap the number of permits issued to climb the mountain. It comes as the tourism-dependent country marked the anniversary this week of the first ascent of Mt Everest by Edmund Hillary and Tenzing Norgay in 1953.
