What are the tests for ritalin (methylphenidate) overdose?

Professional eval. There are no tests, and an expert physician would not need tests. An "overdose" (other than deliberate) is a relative thing. Whomever is prescribing the Ritalin (methylphenidate) needs to discuss your experience with the medication, including benefits and possible problems. Meds of this type always need close clinical monitoring, especially in the early stages and when doses, or circumstances, change.