The Queen's physician Dr. Huw Thomas said Philip died of "old age" rather than any one condition on his death certificate, which The Telegraph obtained.
The paper said this was an accepted cause of death if a person is over the age of 80 and if the doctor has personally cared for the person for a long duration and observed a gradual decline.
Prince Philip died at the age of 99 at Windsor Castle on April 9 after being hospitalized for four weeks in February and March.
He was treated for an infection and a preexisting heart condition before being discharged March 16.
He was also hospitalized in December 2019 for a preexisting condition, a palace representative said at the time, and in June 2017 for treatment for an infection.