The insulin autoimmune syndrome is characterized as producing polyclonal or monoclonal anti-insulin autoantibodies in a patient with no previous history of exposure to exogenous insulin. The patient is 44-year-old Japanese woman and she had symptoms of hypoglycaemia without exposure to exogenous insulin. The patient was considered to have IAS because high titre of anti-insulin autoantibodies (96-98%: bound/total) were found in her serum. Her HLA DR beta1 DNA sequences analysis revealed that she has the DRB1(*)0406 and DRB1(*)0901. Our patient have been taken alpha lipoic acid (ALA) before onset. SH group compounds are known to play an important role in the pathogenesis of IAS, and ALA contains SH. From these data, we propose the possibility of the correlation between pathogenesis of IAS and ALA, and it will be important to pay attention for ALA as a cause of hypoglycemia in such cases.