The purpose of this study is to see if it is safe and effective to give alpha lipoic acid in people with cardiac autonomic neuropathy(CAN). Cardiac autonomic neuropathy(CAN) affects the nerves that control heart rate and blood flow to the heart in people with diabetes. CAN may cause problems with the rhythm of the heartbeat or decrease blood flow to the heart.

Study type : Interventional Study Design : Allocation: Randomized Control: no treatment Endpoint Classification: Safety/Efficacy Study Intervention Model: Parallel Assignment Masking: Open Label Primary Purpose: Treatment Primary Outcome Measures : Heart rate variability(HRV) Index

Secondary Outcome Measures : Autonomic Nerve System(ANS) function 5 test, EuroQoL 5-Dimension Questionnaire(EQ-5D)

Inclusion Criteria :

• Established Cardiac Autonomic Neuropathy in type 2 diabetes.
• aged 20 years to 80 years
• Capable of giving informed consent

Exclusion Criteria :

• History of other significant disease such as the nerve system (Parkinson's disease, epilepsy, multiple sclerosis), hepatic disease, hypothyroid, etc Other medical condition or treatment likely to affect the autonomic nerve system
• HbA1C > 11%
• Not controlled hypertension (SBP≥160mmHg, DBP≥100mmHg)
• Diagnosed ketoacidosis within 4 weeks
• Unstable cardiac disease (unstable angina or myocardial infarction )
• Pregnancy
• Involvement in other clinical trial in last 4 weeks
• Known or suspected sensitivity to trial products