Niacin tablets are vitamin-based medicines used for the prevention and treatment of niacin deficiency and are generally harmless, but side effects such as reddening of the skin, dizziness, and fatigue may occur after taking them. General adverse reactions to niacin tablets include feeling warm, redness of the skin, especially on the face and neck, headache and other vasodilatory reactions. Generally after taking niacin for 2 weeks, vasodilatation and gastrointestinal discomfort can be gradually adapted, and the above reactions can be avoided by gradually increasing the dosage. In case of severe skin flushing, pruritus, gastrointestinal discomfort, the dose should be reduced. Large doses may also cause diarrhea, dizziness, fatigue, dry skin, itching, dry eyes, nausea, vomiting, stomach pain, hyperglycemia, hyperuricemia, cardiac arrhythmia, and hepatotoxic reactions. It is recommended to drink more water, eat more fresh vegetables and fruits, generally with the strength of the drug, the side effects will gradually disappear, if there is serious discomfort, it is recommended to go to the hospital in time to seek medical attention.