Abstract: Objective To deepen the understanding of hypomagnesemia caused by alcoholism that aggravate neuropathy in clinical practice by reporting one diabetic patient with hypomagnesemia caused by excessive drinking. Methods The case was a 53 year-old male with chronic alcohol abuse for years. He admitted to our hospital in Oct 2017, presented with ashyperglycemia and progressive numbness in the hands and feet for 7 years combined with amyotrophy for 1 year. He was alcoholism for years.Neuroelectrophysiological examination indicated a peripheral nerve injury, electrocardiogram revealed T wave changes, and brain MRI showed brain atrophy. Hypomagnesemia was ignored for many years. Results The patient complained of hand and foot numbness, progressive weakness, muscle atrophy in lower limb, which first diagnosed as diabetic neuropathy, alcoholism associated thiamine deficiency. After giving the medication such as vitamins B and lipoic acid, no obvious effect was observed. Then we reviewed the whole medical history and realized hypomagnesemia by alcoholism which we neglected before. Combined with neuroreophic drug, magnesia was given (500 mg/d), and then the symptoms of weakness and numbness were alleviated. Conclusion When weakness, numbness in the hands and feet presented in patients with diabetic and alcoholism, not only diabetic neuropathy and thiamine deficiency should be considered, but hypomagnesemia caused by alcoholism should not be ignored.