WASHINGTON (CNN) -- Sen. Thom Tillis was hospitalized Wednesday morning after having a medical episode while running in the annual American Council of Life Capital Challenge race in Washington, but the North Carolina Republican said later he's "doing well."
Event spokesperson Jeff Darman said Tillis suffered a seizure and was transported to George Washington University Hospital. The senator was alert when medical responders arrived on the scene, he said.
Tillis later tweeted a written message and video of him in a hospital bed.
"I'm doing well. Looking forward to getting back to work. Thanks for all of your prayers and well wishes. #CapChallenge," Tillis wrote on Twitter.
In the video, Tillis said he was "overheated" and that "no CPR" or "special measures" were needed. He did not say whether he'd had a seizure.
"Hey everybody. I'm fine. Just running about 2 and half miles in, got overheated, no CPR, no special measures, just checking me out," Tillis said in the video. "See you back on the Hill."
Tillis, 56, was first elected to the Senate in 2014, after serving as speaker of North Carolina's House of Representatives. He sits on several high-profile committees in the Senate, including armed services, judiciary and veterans' affairs.
Gov. Roy Cooper of North Carolina, a Democrat, tweeted well wishes to Tillis.
"My thoughts and prayers are with Senator Tillis and his family. - RC" he tweeted.
His Senate colleagues also sent him prayers.
"Please pray for my Senate colleague @ThomTillis" Sen. Marco Rubio tweeted.
Several members of Congress planned to run in the annual three-mile road race, including Georgia Republican Rep. Tom Graves, Sen. Tom Cotton of Arkansas and Sen. John Cornyn of Texas.