Hai, Loss of weight is one of the symptom of diabetes. Once your diabetes is under control then the significant weight loss issue will be cleared out and solved. As your BMI says you are underweight. if you didn t feel anything abnormal with your physical and mental status kindly ignore temporarily regarding your weight loss. concentrate in controlling your sugar level. However,you can take protein rich food like almond,peanut,soyabean,fig regularly in your diet to increase your weight on the other hand keeping a check on your sugar level too. visit a dietician to have a menu for both weight gain as well as low glycemic foods. thank you hope i answered your query thank you hope i answered your query