Niki Lauda is reportedly back in hospital receiving dialysis treatment for further kidney problems.
The 70-year old was recovering from a bout of flu last year and was aiming for a return to the F1 paddock soon until this latest setback.
Austrian newspaper Osterreich have reported that Lauda is in a private clinic in Switzerland.
Lauda’s brother Florian confirmed the news, saying: "Due to kidney problems, he had to be transferred from the rehabilitation centre to a private clinic for dialysis."
Mercedes team boss Toto Wolff added: "Niki has good weeks and also some setbacks.”