Often people take vitamins as nutrients, or even as health supplements, thinking that more is better. Although the toxicity of vitamins is very low, vitamin poisoning can occur if they are taken improperly or in excessive amounts. The vitamin debate began in the 1970s, yet vitamins are still widely used, with 10-20% of adults in Europe and the United States taking them on a long-term basis. For example, chronic intake of vitamin A by pregnant women at levels slightly above the recommended daily intake can cause fetal birth defects and liver damage. If vitamin A is taken in large amounts over a long period of time, it can cause damage to various parts of the body, including the eyes, bone and blood, skin, central nervous system, liver, and reproductive, urinary, and motor systems, with toxic reactions such as dizziness, vomiting, headaches, skin damage, mental retardation, and menstrual disorders. Long-term intake of vitamin A in children at the recommended daily intake for adults can cause liver damage; excessive intake of vitamin B3 can lead to flushing of the skin on the face and shoulders, headaches, itching and stomach problems, and significant overdose can lead to oral ulcers, diabetes and liver damage; vitamin C is highly acidic and should not be taken in large doses on an empty stomach to avoid stomach irritation or stomach ulcers. Long-term overdose of vitamin C (such as 1000mg per day) will not only fail to ward off diseases, but also lead to headaches and kidney stones; long-term overdose of vitamin D can cause hypercalcemia, loss of appetite, weakness, vomiting, diarrhea, and even soft tissue ectopic calcification, myelosclerosis, liver enlargement, etc. Excess calcium may be deposited in the kidneys, causing damage to the kidneys and causing hypertension or kidney stones; Long-term overdose of vitamin E will make the body easily fatigued and diarrhea, which may cause bleeding; long-term overdose of vitamin K will damage liver function, and should not be taken by patients with liver. Therefore, vitamins should not be applied as supplements, and should be taken under the guidance of a doctor, not to mention that the dose should not be increased at will, especially for children, the dose of vitamin D and vitamin A should be strictly controlled to prevent adverse drug reactions.