The total serum fucose level in diabetic patients is slightly increased in comparison with normal healthy subjects, mainly due to the presence of non protein-bound fucose. The serum fucose content after glucose loading does not show any difference between controls and potential diabetics (prediabetics). The determination of total serum fucose in patients with hyperglycemia may be complicated by the elevated blood glucose and it is necessary to use the method of internal standardization to avoid a possible error.