The benefits of vitamin C, especially the beauty benefits, often tempt us to fully supplement vitamin C, but you should carefully study the following points. If you don't supplement it well, it will be counterproductive! 1, excessive intake of vitamin C may cause the formation of oxalic acid and uric acid stones (intake of calcium, vitamin B6 and drinking enough water every day can be adjusted). Excessive intake will cause some uncomfortable side effects, such as diarrhea, polyuria, rash and so on. When you have the above symptoms, you must reduce the amount. 2. Cancer patients who are receiving radiotherapy or chemotherapy should not take vitamin C..3. Vitiligo patients should not use vitamin C.