The present invention relates to a method for washing laundry during a washing cycle in a laundry washing machine (1) comprising a washing drum (4); a washing tub (3) external to the washing drum (4); a water supply unit (5) to supply water (W) into the washing tub (3); an automatic dosing device (58) comprising a compartment suitable for receiving a quantity of detergent (D) sufficient for a plurality of washing cycles; a recirculation circuit (30) and a concentration sensor device (80). The method comprises the steps of: introducing a first prefixed quantity (Q1d) of detergent (D) and a first prefixed quantity (Q1w) of water (W) into the washing tub (3); activating the recirculation circuit (30) for mixing the first prefixed quantity (Q1d) of detergent (D) with the first prefixed quantity (Q1w) of water (W); determining the current concentration value (V) of the detergent (D); comparing the current concentration value (V) with one or more prefixed concentration levels (T1, T2) and either introducing or not
