An optical test strip for measuring an analyte concentration in a sample of bodily fluid, comprising: a) a bottom layer having a first end, wherein the bottom layer is at least one layer of the test strip arranged at a bottom side of the test strip; b) a top layer having a first end essentially aligned with the first end of the bottom layer, wherein the top layer comprises at least one top foil, wherein the top foil is transparent; c) at least one spacer layer interposed between the bottom layer and the top layer, the spacer layer having a length shorter than the bottom layer and shorter than the top layer such that the top layer and the bottom layer protrude over the spacer layer, wherein the first end of the bottom layer, the first end of the top layer, and the spacer layer form a sample receiving area which at least partially has capillary properties for receiving the sample of bodily fluid; and d) at least one test field, wherein the test field is attached to the top layer, wherein the test field comprises a test chemical being configured for performing an optically detectable detection reaction with the analyte, wherein the test field comprises at least one first region and at least one second region, wherein the first region and the second region have essentially the same spectral and/or spectroscopic characteristics and/or reflective and/or absorption properties, wherein the first region faces the sample receiving area, wherein the first region is configured to be at least partly wetted by the sample of bodily fluid upon sample application, wherein the test strip comprises a layer setup, wherein the test strip has a top side and the bottom side, wherein the top side is the side from which the test field is accessible for image capturing, wherein the top layer is a layer of the test strip confining the layer setup of the test strip at the top side of the test strip, wherein the second region is covered by the spacer layer such that the second region is essentially inaccessible for the sample of bodily fluid, wherein the first region and the second region are arranged successively along an elongated extension of the test strip. a) a bottom layer having a first end, wherein the bottom layer is at least one layer of the test strip arranged at a bottom side of the test strip; b) a top layer having a first end essentially aligned with the first end of the bottom layer, wherein the top layer comprises at least one top foil, wherein the top foil is transparent; c) at least one spacer layer interposed between the bottom layer and the top layer, the spacer layer having a length shorter than the bottom layer and shorter than the top layer such that the top layer and the bottom layer protrude over the spacer layer, wherein the first end of the bottom layer, the first end of the top layer, and the spacer layer form a sample receiving area which at least partially has capillary properties for receiving the sample of bodily fluid; and d) at least one test field, wherein the test field is attached to the top layer, wherein the test field comprises a test chemical being configured for performing an optically detectable detection reaction with the analyte, wherein the test field comprises at least one first region and at least one second region, wherein the first region and the second region have essentially the same spectral and/or spectroscopic characteristics and/or reflective and/or absorption properties, wherein the first region faces the sample receiving area, wherein the first region is configured to be at least partly wetted by the sample of bodily fluid upon sample application, wherein the test strip comprises a layer setup, wherein the test strip has a top side and the bottom side, wherein the top side is the side from which the test field is accessible for image capturing, wherein the top layer is a layer of the test strip confining the layer setup of the test strip at the top side of the test strip, wherein the second region is covered by the spacer layer such that the second region is essentially inaccessible for the sample of bodily fluid, wherein the first region and the second region are arranged successively along an elongated extension of the test strip. wherein the test strip comprises a layer setup, wherein the test strip has a top side and the bottom side, wherein the top side is the side from which the test field is accessible for image capturing, wherein the top layer is a layer of the test strip confining the layer setup of the test strip at the top side of the test strip, wherein the second region is covered by the spacer layer such that the second region is essentially inaccessible for the sample of bodily fluid, wherein the first region and the second region are arranged successively along an elongated extension of the test strip.