Diabetic patients are prone to B vitamin deficiency and may take appropriate supplementation based on nutritional assessment. Diabetic patients without B vitamin deficiencies do not require long-term supplementation with large amounts of B vitamins. Vitamin B12 deficiency should be prevented in diabetic patients on long-term metformin. In addition to B vitamins, diabetic patients should also be aware of deficiencies of vitamin C, vitamin D, and many micronutrients such as chromium, zinc, selenium, magnesium, iron, and manganese. Diabetic patients without micronutrient deficiencies do not need to be supplemented with large quantities of vitamins, micronutrients, and preparations such as plant extracts for long periods of time, and their long-term safety and improved clinical outcomes have yet to be demonstrated. Diabetic patients who need to supplement B vitamins should do so appropriately under the guidance of their medical professionals.