Lord Lloyd-Webber said he was tempted to end his life last summer as he fought the pain of 14 operations.
In an interview with the Daily Telegraph, the 66-year-old said he could think of little else other than taking his own life during that bleak period, but now believes that to do so would have been "stupid and ridiculous".
And he said he was "unsure" of his own stance over assisted dying, as peers debate Lord Falconer's Bill in the House of Lords today.
The composer said his mother had decided five years before her death in 1993 that she wanted to die to avoid become a burden to her sons, Andrew and Julian.
Lord Lloyd-Webber said he felt his mother was in no way ready to die, but that, had the law allowed it, she would have gone through with it.
Lord Lloyd-Webber revealed that he found he shared her wish after dealing with the painful consequences of repeated medical procedures following a back operation.
He told the newspaper: "There were days when I thought that I would do anything to get out of this. I adore my work, and I thought that if I could not do that, then I had nothing more. I went through a moment of deep depression - that awful moment when you think that you must find a way out.
"I actually got the forms for Dignitas. With hindsight, it was stupid and ridiculous, but I couldn't think what to do."
In the end, he said, he threw the forms away and found relief through a chiropractor.
Lord Lloyd-Webber will be in the Lords to listen to the debate today, but is undecided on his own opinion.
He told the Telegraph: "If people get to a point where their lives are so impossible, I would agree with the Bill. What concerns me, and I suspect many others, is what floodgates would (this measure) open?
"Does it create a culture where older people are a burden? In 20 years' time, signing off on the deaths of old people might not be taken as seriously as it is now. I am totally unsure."
The late MSP Margo MacDonald made two unsuccesful attempts to change the law on assisted dying in Scotland.