We characterized Mexican honey from the main production regions, using the internal stable carbon isotope ratio (ISIRA) of the honey and its protein. We found the average δ13C given by White for American honey is very close to the corresponding value for Mexican honey, even though clear evidence that C4 and CAM plants are visited by bees. We found adulteration of Mexican commercial samples using the criterium of -1.00 ‰ difference also given by White. Two pyrolysis methods were tested to optimize the accuracy of the carbon isotope ratio analysis of honey. We found that the quartz method showed smaller variation in the data due to a complete combustion of the honey. The honey protein was isolated and purified using the protein dialysis procedure recommended by the Association of Official Analytical Chemists. We found that the direct precipitation method without dialysis is not useful for samples which are adulterated by more than 50%.