The 18-year-old man is believed to have been struck by a vehicle near Bellshill and is being treated for serious injuries at the intensive care unit at Glasgow Royal Infirmary.
A spokeswoman for Police Scotland told the BBC: “Around 1100 hours on Tuesday 22nd November, police attended a report of an 18-year old man having sustained serious injuries whilst working at the M8 road works near to Carnbroe Road, Bellshill.
“Emergency services responded and the man was taken by ambulance to Glasgow Royal Infirmary.
“The injured man is still within the intensive care unit after receiving treatment for serious injuries. His condition is critical but stable.
“The incident is being treated as an industrial accident and as such a full investigation will be undertaken by Health and Safety Executive.”