The 'Careless Whisper' hitmaker was due to pick up the Icon Award at Attitude magazine's prize giving, where Ian McKellen, Lady Gaga and Gary Barlow also won top honours, reported Daily Express.
"George must put his health first," said the magazine's editor Matthew Todd.
The 49-year-old's illness comes just two weeks after he announced he is cancelling a series of shows in Australia to focus on his health and to seek treatment for "anxiety" issues.