 Flushing is the most common side effect of niacin. Other side effects include gastrointestinal disorders common diarrhoea, nausea, vomiting, abdominal pain, or dyspepsia and cardiac disorders uncommon tachycardia, palpitations. A reversible elevation of liver enzymes has been reported, as well as a decreased glucose tolerance, reductions in platelet counts, increases in prothrombin time, elevations in uric acid levels, and reductions in phosphorous levels uncommon or rarely. Hypersensitivity reactions have been reported very rarely. 