A 76-year-old Chinese female presented by ambulance to the Emergency Department complaining of dizziness, headache and fatigue. Her son claimed that the patient “turned blue” three hours prior to onset of the patient’s symptoms. Paramedics noted the patient’s SpO2 was 83% on room air with no improvement with a non- rebreather mask. Past medical history was significant for diabetes and hypertension. Family, social and medication history were non-contributory. Patient denied ingestion of any traditional Chinese medicines but did have some choy sum (a variety of green vegetable) for lunch five hours prior to arrival. On examination, the patient appeared agitated, but alert. Purple lips and fingers were noted (Figure 1). Physical examination: heart rate 55 beats/minute, pulse oximetry 87%, respiratory rate 16 breaths/minute, blood pressure 143/51 mmHg. Bedside investigations: chest X-ray (clear lung fields and cardiomegaly); ECG (sinus rhythm, slight bradycardia at 53 beats/minute); hemoglobin 9.3 g/dL; glucose 10.9 mmol/L (196.2 mg/dL).