The Grammy Award winner, 74, was performing at the outdoor Pine Knob Music Theatre in Clarkston, Michigan when the incident happened. A statement on his website said he was taken to the emergency department at McLaren Clarkston medical centre for observation and was doing well.
"To one and all, thank you for your precious prayers. Cindy and I we are good just taking it easy," Santana wrote on his Facebook page, referring to his wife, drummer Cindy Blackman.
"Forgot to eat and drink water so I dehydrated and passed out, blessings and miracles to you all."
Footage from the concert showed medical personnel and other crew huddled around Santana on stage.
The statement quoted Santana's manager, Michael Vrionis, as saying the guitarist's show on Wednesday in Burgettstown, Pennsylvania would be postponed to a later date.
Known for hits like "Black Magic Woman" and "Oye Como Va", Mexican-born Santana, who rose to fame in the late 1960s with his band Santana, is currently on his "Miraculous Supernatural 2022 Tour".