However, the 86-year-old former astronaut is said to be 'responding well' to the treatment for fluid on his lungs at Christchurch Hospital, New Zealand, and is in stable condition.
Aldrin was visiting the South Pole as part of a private tourist group when his health deteriorated.
It said he was taken on the first available flight to McMurdo Station, a US Research center on the Antarctic coast.
He currently has fluid in his lungs but is responding well to antibiotics and being kept overnight for observation," travel company White Desert said in a statement.
Aldrin became the second man to walk on the moon in 1969 as part of the US Apollo 11 mission.
(With Agency inputs)