The K-LACGAR kit measures lactose by measuring the galactose released from lactose however this assay also measures the free galactose present before any lactose is hydrolysed.
Therefore K-LACGAR is not adversely affected by free galactose in the samples. The assay and calculation accounts for this. For high levels of galactose then procedure B in the kit booklet can be used to lower this so it is not an issue in the measurement of lactose.