Former First Lady Lucy Kibaki was on Friday admitted to Nairobi Hospital.
There were conflicting reports about her condition, with a family spokesman saying she was at the health institution for routine check-up.
Other sources said she was in the intensive care unit.
The hospital declined to give any information, citing doctor-patient confidentiality. The authorities referred journalists to the family.
Mrs Kibaki is said to have been taken to the hospital around 5am. Staff on duty did not immediately recognise her because of the low-key nature of the admission, a source said.
Other reports say she was first treated at Gertrude’s Hospital, which is near her home, before being transferred to Nairobi Hospital.
“There should be no alarm at all. It is merely a routine check-up; the kind that your mother and mine would need to undergo from time to time. Remember our mothers’ health, given their age, cannot be the same as that of high school girls,” former President Mwai Kibaki’s press secretary, Dr Ngare Gituku, said in response to questions from journalists.
There were no signs of unusual security detail to show the presence of a VIP at Nairobi Hospital, although unconfirmed reports say Mr Kibaki’s eldest son Jimmy and other members of the family had visited the facility at different times during the day.
A woman whose relative is in the ICU said they were asked to leave the area around 1pm “and we saw the Kibaki family entering”.
“I wish they had announced to us that they would not allow anyone in. They asked us to step aside and the door was locked. We have been knocking at the door with no response,” she said.
Mrs Kibaki has not been seen in public for nearly five years.
Her last public function was on August 27, 2010, during the promulgation of the Constitution, where she appeared excited as she danced along to Emmy Kosgei’s hit “Taunet ne lel” (Kalenjin for a new beginning).
Dressed in black and a gold sash, and accompanied by one of her grandsons, she was seen chatting with her husband and breaking into laughter.