The invention provides a kit for a glycated haemoglobin assay, said kit comprising : a porous membrane capable of retaining precipitated haemoglobin ; a first reagent comprising zinc ions in aqueous basic solution or comprising a water soluble zinc compound ; a second reagent comprising a chromophore-boronic acid conjugate ; and optionally, an aqueous washing reagent ; wherein at least one of the first and second reagents further comprises a surfactant capable of lysing erythrocytes, and wherein said second reagent if liquid is acidic.
