Withdrawal? Only patients with diabetes take insulin. If they stop taking it, then blood sugars go up very high and may cause a life-threatening metabolic emergency called, diabetic ketoacidosis (dka). Though patients with type 2 diabetes don't normally get dka, high blood sugars will cause other problems.
Not a withdraw. Withdraw from Insulin is not realy correct term. If sombody needs inuslin for treatmet of diabetes but stopping it glucose will increase and may reach "hyperglycemia" causing dehydration, mental alteration, up to coma. Inulin adjustment should be always under medical supervision.