"He had an episode, he was light-headed and dizzy," Texans general manager Rick Smith said after the game. "He was evaluated by a number of specialists. ... He is awake and coherent.
"He went to a knee, and they laid him on the ground. He is stable; for precautionary reasons we wanted to get him to the hospital. We have to assess ... obviously, there's a lot of info. Hopefully, Gary will be back with us tomorrow."
Andrew Luck got off to a slow start before throwing three second-half touchdowns to T.Y. Hilton to overcome an 18-point halftime deficit and give the AFC-South-leading Colts (6-2) the victory.
Case Keenum threw for 350 yards and three touchdowns in his second career start, but had trouble moving the offense after halftime as the Texans, up 21-3 when Kubiak collapsed, lost their sixth straight game after opening the season 2-0 with Super Bowl hopes.
Houston had a chance to tie it, but Randy Bullock's 55-yard field-goal attempt as time expired sailed wide left.
The Colts took their first lead of the game when Hilton grabbed a 9-yard touchdown reception and Coby Fleener caught the 2-point conversion to make it 27-24 with 4 minutes left.
Bullock missed a field goal early in the fourth quarter, and the Colts cut it to 24-19 when Luck found Hilton on a 58-yard touchdown pass two plays later.
Houston built the halftime on Keenum's three touchdown passes to Andre Johnson. Johnson had 190 yards receiving at halftime but just 39 yards after that.