The This Morning host, a close friend of the Australian actor, recalled telling Donovan's wife Angela Malloch that he feared the worst.
Schofield, speaking on a VT in Piers Morgan's Life Stories, says: "Jason was at the time quite often chemically assisted.
"On a couple of occasions I went out for lunch with him and the next day he wouldn't remember where we'd been or the fact that we'd met up.
"It was a shame to see someone who was always so handsome and adored, essentially coming apart at the seams.
"I can remember saying to my wife, 'You know we should do something, there must be something we can do to help', because, I thought, eventually this is going to end up in tragedy.
"He wouldn't be the first or last in that line of people who had everything at their feet and had taken the wrong track and ended up killing themselves."
Jason Donovan's appearance on Piers Morgan's Life Stories, which sees the former Neighbours star admit that drugs still tempt him, airs tonight at 9pm on ITV1.