The audience at the London Palladium was told that the 76-year-old entertainer, who has been battling a chronic lung disease, would not be performing as planned because he was unwell.
But Candi Cazau, a spokeswoman for the Las Vegas showroom where Lewis has a long-term contract to perform, denied that he had collapsed, as was reported in some media accounts.
Cazau said Lewis was in his dressing room at the Palladium, the theater where he first appeared with Dean Martin some 50 years ago, when he "got a little dizzy."
As a precaution, medical personnel were summoned to examine him, "and everything checked out OK," she said. "He didn't even go to the hospital. He's absolutely fine." She added that he is expected back in the U.S. Tuesday.
Word of Lewis' illness came a few hours before the London Daily Mirror printed an interview quoting the entertainer as saying the pain from his various physical ailments has been so intense, he bought a gun last spring and considered killing himself.
Cazau said Lewis had been following a "vigorous schedule" in recent weeks, preparing for and performing at last weekend's annual Labor Day Telethon for muscular dystrophy, and flying to London a few days later.
A visibly bloated Lewis appeared for about eight hours of the 21-hour telecast, which raised about $58 million for the Muscular Dystrophy Association.
Cazau said Lewis had gained about 50 pounds from the steroids he was taking as a treatment for pulmonary fibrosis, an inflammatory lung disorder. She said doctors recently began gradually weaning the comedian off the medication.
"He's in excellent spirits" and has numerous speaking engagements booked for November, she said. Cazau said Lewis may resume his live performances at the Orleans Hotel and Casino next year and is still working on a memoir of his days with the late Dean Martin.
The comedian has been plagued with health problems for decades. Back in the 1980s, he was declared clinically dead after suffering a heart attack. He later had prostate cancer, was diagnosed with diabetes and suffered from spinal meningitis.
Earlier this year, Lewis underwent surgery to implant a battery-powered device designed to ease chronic back pain he had suffered from years of pratfalls.
Last year, Lewis cut back the hours he spends hosting the telethon because he was recuperating from a bout of pneumonia. The year before, a case of viral meningitis forced him to sit out much of the show.