A 43-year-old male with a history of metastatic undifferentiated pleomorphic sarcoma (UPS), hypertension, hypothyroidism, and depression presented to the outpatient clinic for a regularly scheduled blood draw. The patient reported new-onset symptoms of decreased appetite over the preceding 3 weeks, accompanied by weight loss, frequent urination, dry mouth, and insatiable thirst over the previous 4 days. To evaluate these symptoms, the patient’s provider requested that a serum glucose measurement be performed. The patient had no previous history of hyperglycemia or diabetes and his last glucose measurement 1 year prior was 114 mg/dL. Leading up to this encounter, the patient had been receiving intravenous infusions of pembrolizumab every 3 weeks for 2 years to treat his UPS. His outpatient medications included levothyroxine, sertraline, hydrochlorothiazide, and amlodipine.