Former Emperor Akihito temporarily lost consciousness and collapsed at his Tokyo residence on Wednesday but a subsequent medical checkup found no abnormalities, the Imperial Household Agency said Thursday.
The 86-year-old's condition is back to normal and he had breakfast as usual on Thursday morning, according to the agency.
Former Empress Michiko, who was nearby when her husband collapsed, supported the former emperor and called a doctor by activating an emergency alarm.
When the doctor arrived at the scene, the former emperor was still unconscious and snoring, according to the agency.
After regaining consciousness, he was moved to his bedroom where the doctor provided treatment.
The former emperor underwent a magnetic resonance imaging scan on his head Thursday morning that found no abnormalities.
In July, he suffered a bout of cerebral anemia at his residence while having dinner, which forced him to postpone a regular health checkup, but he quickly recovered.
The former emperor abdicated at the end of April last year as the first monarch in the country to step down in about 200 years, and his son Emperor Naruhito ascended the throne the following day.