Seven-time Formula One champion Schumacher suffered brain injuries after a skiing accident in the French Alps in December 2013.
He was placed in a medically induced coma for six months before he was eventually moved to a rehabilitation ward after regaining consciousness in June 2014.
Doctors believe the former Ferrari and McLaren ace would probably have died had he not been wearing a helmet.
In 2014 Schumacher, 49, was moved to the family home near Lake Geneva in Switzerland, where he receives round-the-clock care from a team of specialists.
Wife Corrina, 47, son Mick, 19, and daughter Gina-Maria, 21, rarely discuss his condition in the years since the tragedy.
But manager Sabine Kehm said they were grateful for all the support.
She said: “What can be said is that the family really appreciates the empathy of the fans.
“The people really do see and understand (his health situation) is not to be shared in the public eye.”
Since his accident, rumours have suggested Schumacher had slowly started walking again, and that the cost of his treatment was in excess of £20million and counting – but his family has consistently refused to discuss the matter,
In a statement issued 16 month ago, Mrs Kehm insisted: “Michael’s health is not a public issue, and so we will continue to make no comment in that regard.
“Legally seen and in the longer term, every statement related to his health would diminish the extent of his intimate sphere.”
Fans regularly post messages on his Facebook page asking how he is.
A poll by the Wheels24 website suggested that 58per cent of his fans would “like to know it he’s okay”.
Friends and former colleagues have also pleaded with his relatives for more information.
Talking with the German newspaper TZ last year, former manager Willi Weber, said: “I find it very unfortunate that Michael’s fans do not know about his health. Why are they not told the truth?”
Schumacher’s health may be a mystery but motor racing fans will surely never forget his accomplishments.
The update comes as the F1 drivers prepare to start a new season in Australia this weekend, following a three month break.
On an F1 track near Barcelona this month, a red flag flying above a grandstand facing Ferrari’s garage read MICHAEL FOREVER – in recognition of his five titles with them between 2000 and 2004.
The German quit F1 in 2006 after finishing second to Fernando Alonso by only 13 points in a bid for an eighth title.