The 1992 Melbourne Cup winner Subzero is under veterinary care because of weight loss and a reduced appetite.

The much-loved rising 25-year-old, who worked as clerk-of-the-course horse for 15 years after retiring from the racetrack, has been examined at the University of Melbourne Veterinary Clinic at Werribee.

Racing Victoria says clinical investigations have identified minor renal insufficiency.

Since retirement from clerk-of-the-course duties, Subzero, under the ownership Graham Salisbury, visits schools all around Victoria and even has his own line of merchandise.

Salisbury said the popular grey was in good spirits.

"Subzero's not going backwards, he's in good spirits and walking about," Salisbury said.

"He's a racing legend who has touched hearts of lots of people throughout his life."

Subzero was bought at the Magic Millions sales to be a sprinter but under the guidance of Hall of Fame trainer Lee Freedman he soon stamped himself as a promising stayer.

That potential was realised during an autumn campaign in 1992 with wins in the South Australian Derby and the Adelaide Cup.

Freedman gave Subzero what was then a traditional Melbourne Cup preparation with a sequence of weight-for-age runs and a Caulfield Cup start.

On a deteriorating track, Subzero defeated New Zealand stayers Veandercross and Castletown in the Melbourne Cup.

It turned out to be the last of his six wins and he was retired from racing after the 1994 Brisbane Cup with earnings of more than $2 million.