Functional food for lactose-intolerant consumers and its global prevalence has created a large market for commercially available lactose-free food products. The simplest approach for detection and quantitation of lactose in lactose-free dairy products was developed. A one-step sample preparation was employed and the resulting 10% sample solution was directly subjected to the chromatographic system. LODs down to 0.04 mg/L were obtained for dairy products by application volumes up to 250 μL on a rectangular start zone, which is the lowest LOD reported in matrix so far. The highly matrix-robust, streamlined approach was demonstrated for a broad range of dairy products, even with high fat and protein contents. The mean recovery rate for 11 types of dairy products spiked at the strictest lactose content discussed (0.01%) was 90.5±10.5% (n=11). The mean repeatability for 11 dairy products spiked at the 0.01% level was 1.3±1.0% (n=11). It is the simplest approach with regard to sample preparation at low running costs (0.3 Euro or 0.4 USD/analysis) and fast analysis time (3 min/analysis). It enabled an efficient product screening, and at the same time, the quantitation of lactose in relevant samples. This streamlined analysis is highly attractive to the field of food safety and quality control of lactose-free dairy products, for which a limit value for lactose is expected soon in the EU. This methodological concept can be transferred to other challenging fields.