Hello! Welcome on Healthcaremagic! The dose of Risperdal that he is taking is not too high. Anyway, if he has been experiencing dizziness after the increase in the dose, he may need to reduce the dose, because this situation could be a sign of intolerance. Further tests are needed to exclude other possible causes of dizziness: - complete blood count for anemia - kidney and liver function tests - fasting glucose - blood electrolytes. A close monitoring of his blood pressure values is also necessary to exclude blood pressure fluctuations, which could trigger this symptomatology. Hope you will find this answer helpful! Kind regards, Dr. Aida