Doctors told the 28-year-old that he had just 24 to 48 hours to live when Brendan Hughes called off the fast to save the life of fellow striker Sean McKenna.
As the days of the first hunger strike rolled on through the autumn and early winter months of 1980, Mr McKearney and his fellow protesters were eventually transferred to the H-Block hospital wing.
"What I found was that from the early days I suffered," Mr McKearney recalled.
"Dispel any thoughts that after a couple or three days people don't feel hunger - I felt it for many of the days until I got very ill.
"The first feeling is coldness and it's very difficult to keep warm.
"We did drink water and a small pinch of salt every day and tried to take as much water as possible."
Mr McKearney said starvation eventually started to take its toll.
"I held up reasonably for about 40 days although I started to feel tired, and weak of course, as muscles and energy levels went down."