Final answer:
The most important statement for the nurse to make is 'You are at risk for increased side effects due to high medication levels.'
Step-by-step explanation:
The most important statement for the nurse to make to a client diagnosed with epilepsy with a carbamazepine level of 11 micrograms/ml is 'You are at risk for increased side effects due to high medication levels.' This statement alerts the client to the potential risks associated with high levels of carbamazepine in their system, such as increased side effects.
It emphasizes the importance of monitoring their medication levels and taking necessary steps to address any concerns with their doctor.