According to Bob Gunnell of Louisville-based Boxcar PR, Ali was admitted to an undisclosed hospital earlier this week.
"Ali hopes to celebrate his 73rd birthday on Saturday at home with his family," Gunnell said on Thursday.
The three-time former heavyweight champion was released from hospital on January 7 after a two week stay for a urinary tract infection.
"The Muhammad Ali family respectfully requests privacy. No further details are being released at this time," Gunnell added.