Doctors told the 71-year-old former Beatle to spend a few days in bed and he's expected to make a full recovery.
"Paul received successful medical treatment at a hospital in Tokyo," McCartney's rep told USA Today.
"He will make a complete recovery and has been ordered to take a few days rest. Paul has been extremely moved by all the messages and well wishes he has received from fans all over the world."
McCartney first announced his illness earlier this week, telling Japanese fans that he wouldn't be able to perform.
"Thank you so much for your kind messages of support," he wrote in a statement. "I'm so very touched. Unfortunately my condition has not improved overnight. I was really hoping that I'd be feeling better today. I'm so disappointed and sorry to be letting my fans down."
McCartney is scheduled to kick off a 19-date tour of the U.S. in Lubbock, Texas on June 14.