The medical check-up led to an unspecified medical procedure during a second hospital stay in early January.
His mother, Wan Tempawan Wan Hanapi, was a Malay of Kedah.
Despite his prominence in UMNO, Mahathir was not a candidate in the 1959 election, ruling himself out following a disagreement with then Prime Minister Tunku Abdul Rahman.
Will you help make that change? On 29 February, the Agong appointed Muhyiddin prime minister, determining that he was "most likely to have received the trust of the majority" of MPs.
He also attracted Anwar Ibrahim, the leader of the ABIM , to join UMNO.
Tun Dr Mahathir to recover quickly.