Hi, thanks for posting your concern in the HCM. The sharp pain at the back of left arm may be due to radiculopathy involving the cervical region. Get a digital X-ray of C-spine (AP & Lateral) done. You may later need to have MRI of C-spine depending upon the findings in your X-ray and clinical examination. A pain of myocardial infarction does radiate to the upper part of the left arm, but it involves the inner aspect and most commonly is associated with central chest pain or retrosternal chest tightness. Still, as you are a long-standing diabetic patient, an ECG should be done. The metallic taste in mouth is caused due to several reasons. Most frequently they are associated with medications because most of the drugs are associated with this adverse effect. Even common cold, nasal infection or sinusitis are associated with this problem. Poor oral hygiene, periodontitis often cause this problem as well. My recommendation is to have citrus fruits for next couple of days and maintenance of good oral hygiene. If the problem still persists, please consult your local doctor for further evaluation and treatment. Finally, overweight in long standing diabetes is definitely a matter of concern for which you should have diabetic diet (with low fat and refined carbohydrate), high dietary fibres and exercise (if possible). For any further query please write back. Regards. Dr. Kaushik