Billy Connolly: High Horse Tour

At the Wilbur Theatre, May 19 at

8 p.m. Tickets: $52, 617-248-9700, www.thewilbur.com

Billy Connolly is one of the best in the world at what he does. For nearly 50 years, ever since he left a career in folk music to make people laugh, he has been traveling the world as a comedian. He’s done TV and film work, but stand-up is what drives him, and it’s made him a rich and satisfied man. When we speak by phone, he is absorbing the afternoon sun outside his home in Malta.

In 2013, he considered giving it all up. He was diagnosed with prostate cancer and then Parkinson’s disease, an incurable, progressive disorder that affects the nervous system. The cancer was the least worrisome of the two — it was removed and Connolly says he’s cancer-free. But the Parkinson’s affects his movement onstage. His doctors and promoter encouraged him to keep performing, but it wasn’t that simple for Connolly.

“I wasn’t quite sure about what to do,’’ he says. “This kind of decision had never been part of my life before. It just hit me like a bombshell, and I thought maybe I should quit. But what am I going to do, look out the window?’’

In the end, he had to do what he’s always done — go onstage and talk about what’s on his mind. The 73-year-old Scot’s date at the Wilbur Theatre May 19 marks the end of a three-city US tour. Living with the disease is part of the act. “The Parkinson’s just rolls along singing a song,’’ he says. “So I keep trying to find lighter things to say about it, because they notice I’ve got it. I walk differently than I used to and I don’t move as much onstage as I used to.’’

He doesn’t want to give away the act, but he gives a little sample of his approach. “I just point out the darker side of it,’’ he says. “Banning Jerry Lee Lewis from the house ’cause he sings ‘Whole Lotta Shakin’.’’

Connolly may not be as animated onstage as he’s been in the past, but his comic storytelling is as nimble as ever. In January, after a show at the Hammersmith Apollo, a Daily Telegraph critic wrote that the comedian was “still somehow in his prime, even as he perhaps approaches his final bow.’’

“It was the best I’ve ever done in London, both the size of the audience and the reception,’’ Connolly says. “The reception was extraordinary. I got a standing ovation going on as well as coming off.’’

That’s partly because Connolly is still trying to get better at his craft. He still gets a small case of nerves before every show, just after he drinks his traditional pre-show coffee. He doesn’t even like coffee, he notes; it just gives him the jolt he needs to get out there. “I think the act of changing into my stage clothes changes my mind into the mind-set I’m going to need onstage,’’ he says. “I’m pretty nervous walking up to the edge of the stage, then when they mention my name, the nerves already have started to go away.’’

He’s a different person onstage. Braver, he says. By necessity. “It’s a strange thing, being a comedian, because you’ve got maybe two or three thousand people in the room,’’ he says. “By walking on, you’re saying you’re funnier than them all. You’re the funniest man in the room, and you’d better do it once you get up there. But it doesn’t do to think about stuff like that, you just go on and enjoy it.’’

Connolly always looks as if there’s something he’s been waiting all day to tell his audience when he arrives onstage. That’s part of what he’s been striving for all these years. “I’ve always tried to speak to them as if they’re one person,’’ he says. “You know, like a funny guy in a bar. And the closer I get to that, the happier I become.’’

His standard isn’t set by other comedians. “It sounds a bit strange, but I’ve tried for years to be as funny as regular people are funny,’’ he says. “Welders and joiners and plumbers and carpenters. Secretaries and nurses.’’

He describes a scene at a bar, around 6 in the evening, where a group of co-workers may have gathered to celebrate someone who’s leaving the company. “If you watch them, they just explode with laughter every five minutes, or every two minutes,’’ he says. “They’re just regular people, don’t think they’re funny, they’re just good at it. And then you go home and you watch television and you see a comedian and you don’t laugh and you go, ‘Ah, he’s very good,’ but you didn’t have the same explosive laughter as the ordinary people in the club. So I’ve always tried to be as good as ordinary people.’’

There is something about the rush of being on tour that Connolly believes staves off his Parkinson’s. He describes being on the road for two or three months at a time and feeling quite healthy. “And then the minute it’s finished, you get sick as if your illnesses are all waiting to happen,’’ he says.

But up there on stage, it can’t touch him. “It’s a miracle,’’ he says. “I think science should study it. I’ve gone on sick and come off better.’’

Billy Connolly: High Horse Tour

At the Wilbur Theatre, May 19 at 8 p.m. Tickets: $52, 617-248-9700, www.thewilbur.com

Nick A. Zaino III can be reached at nick@nickzaino.com.