A 27-year-old female presents with 5 days of elevated mood, decreased sleep (4 hours, feeling rested), increased goal-directed activity, and hypersexual behavior. She has a history of bipolar I disorder, currently on lithium 900 mg and quetiapine 200 mg. Lithium level drawn today is 0.4 mEq/L. What is the MOST likely assessment finding driving this presentation?