Johnson spent three days in the critical unit at St Thomas's Hospital in London and was given oxygen treatment to help him breathe.
Mr Johnson said: "It was a tough old moment, I won't deny it". There was already a strategy for the death: "The doctors had made all possible arrangements of what to do if things went terribly bad".
Mr Johnson, 55, first announced he had contracted COVID-19 on March 27 but maintained he had only mild symptoms.
Johnson said he had received "liters and liters" of oxygen through "the little nose jobbie".
After Johnson was discharged, St Thomas' said it was glad to have cared for the prime minister, but the hospital has given no details about the gravity of his illness beyond stating that he was treated in intensive care.
Mr Johnson, who was hospitalised in early April, described his frustration with the virus, saying how "the bloody indicators kept going in the wrong direction and I thought, "There's no medicine for this thing and there's no cure". - The worst moment was when the doctors were thinking to insert the tube down my throat, the chance was fifty-fifty".
"That's when it started. they were starting to think about how to handle the presentation".
Russian Federation reports 9,623 new COVID-19 cases in a day
Last week, Mr Putin admitted there was a shortage of protective kit for medics on the frontline of the coronavirus crisis. Sobyanin said there had been progress in expanding testing, allowing the authorities to treat those in need more quickly.
He credits his recovery to "some wonderful, wonderful nursing".
Nicholas is in tribute to Dr Nick Price and Dr Nick Hart "the two doctors that saved Boris' life last month", according to Ms Symonds.
Mr Johnson shared his experience of the disease as the number of people to die of COVID-19 in British hospitals, care homes and the wider community rose to 28,131.
"Reality struck me when I was wired up to monitors and moved into intensive care".
Symonds, who works for an ocean conservation charity Oceana, met Johnson during her time as the communications chief for the Conservative Party when he was the Mayor of London in 2012. "Both mother and baby are doing very well", the spokeswoman said at the time.
Johnson has been cautious about easing lockdown measures.
The country has been struggling to keep control of the coronavirus pandemic, with its death toll overtaking Spain and France with over 27,500 deaths - just behind Italy.
Alongside the testing, civil defense authorities set up a contact tracing team, and a mobile phone tracing app was up and running a few weeks later.