An Impaired Awareness of Hypoglycemia Improved After Vitamin B12 Treatment in a Type 1 Diabetic Patient.

An impaired awareness of hypoglycemia is a serious problem in diabetic patients, which can lead to life-threatening severe hypoglycemia. Recurrent hypoglycemia attenuates the function of the central, mainly hypothalamic, nervous system and it causes an impaired awareness of hypoglycemia. Vitamin B12 deficiency is also associated with the dysfunction of central nervous system. We report a 72-year-old type 1 diabetic patient with vitamin B12 deficiency whose impaired awareness of hypoglycemia improved after 4 weeks of vitamin B12 administration with an increased counter-hormone secretion in response to hypoglycemia. We should recognize vitamin B12 deficiency as one of the causes of an impaired awareness of hypoglycemia in diabetic patients.