Berberine-induced hypoglycaemia and electrocardiogram interpretation in athletes

An athletic male in his 40 s presented to the emergency department following a syncopal episode. He was initially found to be hypoglycaemic at 0.9 mmol/L and improved clinically with resuscitation and normalisation of blood sugar. Cardiology was consulted, as his ECG showed sinus bradycardia, incomplete right bundle branch block and first-degree heart block. Medical history revealed that the patient took berberine supplements as a performance-enhancing herbal medication. A literature search showed that berberine-induced hypoglycaemia has previously only been reported in patients with diabetes mellitus. Patients can access non-prescription medicines through online websites and social media without medical counselling and oversight. This case highlights the importance of identifying the cause of new unexplained symptomatic hypoglycaemia, a potentially life-threatening scenario. As shown in this case, a thorough medical history, with special emphasis on supplements and over-the-counter medicines, is often paramount. Importantly, there are many normal ECG variants in different populations. Understanding of the normal ECG variants in athletic individuals is important to avoid over-investigation and diagnosis of cardiac disease. To our knowledge, this is the first case of berberine and exercise-induced hypoglycaemia.