The present invention relates to a lateral flow membrane arrangement (1), comprising a microporous membrane layer (2) and a liquid-impermeable support layer (3), for lateral flow of a liquid through the microporous membrane layer (2), wherein the microporous membrane layer (2) is supported on the liquid-impermeable support layer (3) and has at least one detection zone (5) and at least one non-detection zone, wherein binding agents are immobilized in the at least one detection zone (5), the liquid-impermeable support layer (3) has at least one zone having a large thickness and at least one zone having a small thickness, the microporous membrane layer (2) is supported on the liquid-impermeable support layer (3) such that said at least one detection zone is provided above said at least one zone of the support layer having a large thickness and said at least one non-detection zone is provided above said at least one zone of the support layer having a small thickness, the zones are oriented in a direction orthogonally to the lateral flow direction (a) of said liquid, the detection zone (5) has a thickness (7) of 100 to 150 μm over the entire width of the membrane, the non-detection zone has a thickness (8) of at most 300 μm over the entire width of the membrane, and the lateral flow membrane arrangement (1) has a constant thickness (9), as well as to a lateral flow immunoassay device comprising said membrane arrangement (1).