Hi, welcome to our site. I am Dr Saumya Mittal. Read your query. That is a very significant question and i appreciate your problem. I will try my best to answer your query The possibility is that he is not eating because of the stomach ache. So I should let you know that metformin is known to cause abdominal pain and discomfort. If the pain is persistent you may have to talk to your diabetician to change the medications. There are ofcourse other possibilities. As for diet, he should continue with his diabetic diet as far as possible. This will be important. And you need to step down on medicines if he is not eating. Taking tablets without eating food may cause hypoglycemia. It is always better to have higher sugars than no sugars. Suggest testing urine for ketones and meeting a doctor urgently if the test is positive. Diabetic ketoacidosis may result in abdominal pain and vomitting too I hope this helps you. Inform the reports mentioned above so i can be of help further. Best of luck. I have given you the answer to the maximum considering the information provided. The results of the tests could further enhance my answer to you. Please do understand that some details could be extracted from a detailed history and examination. Looking forward to your return query with the details asked so that I can help you further. Please feel free to ask another query. Would be glad to help you. (If the answer has helped you, please indicate this)