The invention relates to a slide device (1) for ascertaining an amount of insulin to be injected, comprising portions of flat material arranged in layers, which form a disk-like housing body (52), having a plurality of slide tongues displaceable counter to one another, wherein a first slide tongue (8) has a plurality of input scales (16), each with an equidistant line graduation, and a output scale (18), and can be manually grasped for the intended use and is displaceable in a first direction (14) wherein each input scale (16) is assigned a first parameter (37) wherein a second slide tongue (30) is displaceable in a second direction (32), which extends transversely to the first direction (14), and has a window (34) with a setting mark (35), which can be positioned relative to the housing body (52) in such a way that a visual inspection selectively of each of the input scales (16) is enabled wherein next to the second slide tongue (30), a third slide tongue (38) is displaceable in the second direction (32) and has a plurality of windows (40), which are embodied and arranged in such a way that each window (40), in a suitably selectable displacement position of the third slide tongue (38) relative to the housing body (52), enables a visual inspection of the output scale (18) and wherein each window (40) of the third slide tongue (38) on its periphery in the first direction has a reading scale (42) with an equidistant line graduation, and each reading scale (42) is assigned a second parameter (45) and wherein the second slide tongue (30) and the third slide tongue (38) can be placed nondisplaceably in a respective positioning relative to the housing body (52) and wherein after the second and third slide tongues (30, 38) have been positioned, the first slide tongue (8) can be positioned opposite the setting mark (35) at the window (34) of the second slide tongue (30) and then, at a value of the reading scale (42) as a reading mark, a value on the output scale (18) can be
