The ex-Aberdeen, Livingston and United midfielder most recently led Queen’s Park to the League Two title a year ago and is reported to have fallen ill last week.
Many of the clubs he served as a player and as a coach have wished the 51-year-old well online.
Brechin, his first senior club as a boss, wrote: “Everyone associated with Brechin City would like to wish a speedy recovery to former manager Ray McKinnon who unfortunately suffered a heart attack at the tail end of last week. Ray is currently recuperating in hospital. He remains a very good friend of the club and was a special guest at our recent home fixture against Clachnacuddin last month. We sincerely hope that Ray is back to a clean bill of health soon!”
United, where he had two spells as a player and another as manager, said: “Everyone connected with Dundee United would like to wish a speedy recovery to our former player and manager Ray McKinnon. McKinnon is currently in hospital after a recent illness.”
Falkirk echoed: “Everyone at Falkirk football club would like to send our best wishes to former manager Ray McKinnon, who is currently in hospital after a recent illness. We wish Ray a speedy recovery!”
Raith Rovers sent their wishes for a speedy recovery and added: “We are pleased to hear that Ray is currently recovering in hospital. Best wishes Ray #OnceaRover”
McKinnon also spent time as an SFA performance coach and as a player had spells in England at Luton Town and Nottingham Forest.