Psychiatrymiddle twist
A 49-year-old woman with schizophrenia has taken olanzapine for 12 years and attends a community clinic. Over three months she has become thirsty, gets up twice a night to pass urine, and has lost interest in the activities she used to enjoy. Her case manager has recorded the change as worsening negative symptoms. Her weight is up 6 kg over the year, her waist circumference is 108 cm and her blood pressure is 148/92 mmHg. She has had no blood tests for four years. Which one of the following investigations is most likely to reveal the cause of her deterioration?