Abstract: The present invention provides methods for determining the amount of nicotinic acid and its active metabolites in a biological sample using mass spectrometry. The methods involve specific sample collection processes necessary to stabilize and facilitate simultaneous analysis of nicotinic acid and active metabolites. Once in the laboratory, sample preparation is followed by solid phase extraction, liquid chromatographic separation of relevant moieties with detection by MS/MS whereby specific ion transitions are monitored. This invention has several clinical utilities, particularly those related to monitoring patients on antihyperlipidemic drug therapy.