Propranolol has the potential to affect blood glucose. Propranolol competitively antagonizes the effects of isoprenaline and norepinephrine, blocks beta2 receptors, and decreases plasma renin activity. It may cause bronchospasm. It can inhibit insulin secretion, raise blood glucose, mask hypoglycemic symptoms, and delay recovery from hypoglycemia. Propranolol can be used for the treatment of arrhythmia caused by a variety of reasons, but also for the treatment of hypertension, hyperthyroidism, exertional angina and other diseases. Treatment with propranolol is contraindicated in patients who are allergic to propranolol, cardiogenic shock, bronchial asthma, heart block (II-III degree atrioventricular block), severe or acute heart failure, and sinus bradycardia. Patients who require treatment with propranolol should use the drug under the supervision of a doctor.