The 44-year-old, who played Samuel "Screech" Powers in the popular 1990s US school-based sitcom, fell ill last week and was taken to hospital.
His representative, Roger Paul, said the actor is now waiting for further details.
"We will know the severity of it when the tests are done," Paul said, adding they expect an update next week.
Saved by the Bell ran for four seasons from 1989 to 1993 and followed a group of high school friends and their principal.
Diamond reprised his role in follow-up series Saved by the Bell: The New Class, and Saved by the Bell: The College Years. But he did not appear in the recent revival series.
The American was also a contestant on Celebrity Big Brother in 2013.