Gallo Images / Beeld / Felix Dlangamandla
Winnie Madikizela-Mandela was admitted to the Millpark hospital on Wednesday, a spokesperson confirmed.
Madikizela-Mandela, 80, has been admitted for observation, her spokesperson Victor Dlamini told News24 on Thursday.
He was unable to provide any additional information.
Madikizela-Mandela stayed briefly in the Millpark Hospital in December for observation.
In April, she was in a hospital after undergoing back surgery.
Madikizela-Mandela was married to Nelson Mandela for 36 years; the couple were divorced more than 20 years ago in 1996 and he subsequently married Graça Machel.
Madikizela-Mandela has been involved in a legal battle to try to gain control of Mandela's family home in Qunu.