Abstract: Provided, among other things, are methods for treating mammals, such as humans, with diabetes mellitus to delay the onset of end stage renal disease, relating to administering an effective amount of a pharmaceutical composition, wherein said composition comprise, a compound selected from the group consisting of aminoguanidine, its pharmaceutically acceptable salts, and mixtures thereof. Methods are disclosed for the gradual administration of the compound for treatment of diabetes or other indications associated with damage caused by reducing sugars, for the use of a periodic screening test for crescentic glomerulonephritis, and for treating humans with indicia of overt diabetic nephropathy.