The Belgian champion withdrew from the race on Sunday morning after suffering from digestional issues overnight.
"He [Tom Boonen] was up all night with diarrhoea, so there is no point in him starting today," Quick Step team director, Patrick Lefevere, told Cyclingnews on Sunday. "He has been vomiting and he could not eat last night."
The former World champion was only allowed entry into this year's Tour de France a day before the start in Monaco. The French Court of Arbitration for Sport overturned a ban on Boonen starting by race organisers due to a positive test for cocaine.
Boonen has had a difficult time at this year's Tour. A former winner of the green jersey and six Tour stages, Boonen's highest placing at this year's race was 16th on stage 11 in Saint-Fargeau.
Get The Leadout Newsletter
The latest race content, interviews, features, reviews and expert buying guides, direct to your inbox!
