Beta blockers and hypoglycemia

One of the warnings of beta blockers is something called hypoglycemic unawareness. When a person has a low blood sugar they will exhibit symptoms such as tachycardia, diaphoresis, and restlessness. These symptoms are adrenergic mediated. That means that they are due to increases in the adrenergic hormone epinephrine. Beta blockers block the adrenergic receptor. Therefore, if a patient with diabetes has a low blood sugar the symptoms of hypoglycemia may not appear due to the presence of beta blockers. The danger is that the patient will have a dangerously low blood sugar and will not be aware of the problem due to the absence of symptoms.