The 33-year-old Welsh cyclist was involved in an accident with Astana rider Andrey Zeits, with both requiring medical attention on the road.
The crash happened on the fourth stage of the Tour with around 30km to go and occurred shortly after an intermediate sprint, and although Team Ineos confirmed that he was alert and talking despite the heavy impact, he has been forced to abandon what is his final event before the Tour de France.
A statement from Team Ineos on Tuesday read: “As we head into the final 30km of stage four at #TourDeSuisse @GeraintThomas86 has gone down in a crash. Team and race medical personnel are with him now. The Welshman is sat up talking to the team.
““Sadly @GeraintThomas86 has been forced to abandon the #TourDeSuisse. He was alert and speaking to the team after the crash and will be taken to hospital for checks. Further updates to follow.”
Television pictures showed Thomas with cuts and abrasions to his right shoulder and back, but fears of a shoulder or collarbone injury were reduced when he was seen moving both of his shoulders while being treated.
The crash comes six days after four-time champion Chris Froome was ruled out of the tour with extensive injuries from a training crash that included a broken femur, fractured neck, broken ribs and elbow.
Froome suffered a broken neck during his crash on Wednesday and lost approximately four pints of blood, requiring complex surgery that has left him in intensive care.
A six-week spell in hospital will follow after the 34-year-old suffered an accident after taking his hands off the handlebars to blow his nose while travelling at 54 km/h. Scans also showed the six-time Grand Tour winner fractured his right femur, hip, elbow as well as fractured ribs.
After successful surgery, chief surgeon Remi Philippot insisted Froome will be out for “at least six months”.
The incident occurred during a practice ride before stage four of the Criterium du Dauphine in Roanne, France, but the early signs are Froome can make a full recovery, with orthopaedic surgeon Giorgio Gresta claiming he can come back “stronger than before.”