Diabetic patients are prone to vitamin deficiencies, such as B vitamins, vitamin C, vitamin D and some trace elements, such as chromium, zinc, selenium, iron, manganese and many other trace elements, so they can be assessed according to their general nutritional status and supplemented in appropriate amounts according to the results. Patients on long-term metformin should prevent vitamin B12 deficiency. It is generally not recommended in clinical practice to supplement vitamin E, vitamin C, and carotenoids and other preparations with antioxidant effects in large quantities over a long period of time because of the dysregulation of oxidative stress in the onset of diabetes, so the long-term safety of these drugs remains to be further verified if they are taken for a long period of time.