Current Apple CEO Tim Cook offered Steve Jobs a part of his liver when he had become so ill with side effects from cancer that he couldn’t get out of bed, according to a new book.

In “Becoming Steve Jobs: The Evolution of a Reckless Upstart Into a Visionary Leader,” journalist Brent Schlender and Fast Company editor Rick Tetzeli reveal that Cook, upset after visiting the ailing Jobs at his home, was tested to see if he was a match for a potential liver transplant.

Jobs was bedridden and in pain, suffering from ascites, a gastrointestinal condition that causes the belly to swell.

“(Cook) found out that he, like Steve, had a rare blood type, and guessed that it might be the same. He started doing research, and learned that it is possible to transfer a portion of a living person’s liver to someone in need of a transplant,” the authors write in the book, according to an excerpt posted to Fast Company’s website.

Living donors can give a portion of their liver to someone in need. The liver replenishes itself in both donor and recipient within weeks.

Cook visited Jobs at home to offer to be a living donor, but Jobs refused.

"He cut me off at the legs, almost before the words were out of my mouth," Cook is quoted as saying in the book. "'No,' he said. 'I'll never let you do that. I'll never do that.'"

Cook adds that it was one of the “four or five times during the 13 years that I knew him” that Jobs raised his voice at him.

Jobs did eventually have a liver transplant in 2009. He died in October 2011 at the age of 56.

“Becoming Steve Jobs” provides a look at both the business and personal sides of Jobs through interviews with his closest confidants, including Cook.

The book hits store shelves on March 24.