The prince canceled a dinner event planned for Monday evening, the spokeswoman said, adding that other items on his schedule would be dealt with on a "day-to-day" basis. She spoke anonymously, in line with palace policy.
Philip looked healthy recently when he joined the queen in saying goodbye to French President Nicolas Sarkozy and his wife, Carla Bruni-Sarkozy, at the end of their two-day state visit last month.
But he skipped a memorial service Wednesday for Sir Edmund Hillary, the first man to conquer Mount Everest, and has canceled engagements since.
Philip was taken to the hospital late Thursday afternoon but the news was not made public until Friday.
An active man who has enjoyed good health, Philip is known as the queen's constant companion at public events.
A member of the Greek royal family, Philip was evacuated from the country by Britain's Royal Navy in 1922 following the abdication of King Constantine, his uncle. He joined the Royal Navy in 1939 and saw active service throughout World War II.
Philip and Elizabeth married in 1947, when she was still a princess. He gave up his naval career when she became queen and has no constitutional role other than as one of the queen's privy counselors.
Philip is a great-great-grandchild of Queen Victoria.