Santo checked into a hospital after Monday's game against the Pirates. The 70-year-old Santo was feeling the effects of a very hot, muggy day in the broadcast booth.
Santo underwent a battery of tests and no major medical issues were found. A team spokesman said Santo reported that he is feeling much better.
Santo suffers from diabetes and is hoping to return to Chicago on Wednesday when the Cubs leave Pittsburgh.
Judd Sirott filled in Tuesday on WGN. Dave Otto will start filling in for Santo on Wednesday.