Creatinine is a standard marker of renal function as it reflects renal filtration. Elevations in creatinine can be caused by pre-renal causes such as dehydration, renal causes including both acute and chronic renal damage, or post-renal causes, such as urinary tract obstruction. Creatinine is commonly used for diagnostics and incorporated in the IRIS CKD staging and AKI grading, as well as treatment guidelines. The amount of creatinine excreted is, however, very individual and dependent of muscle mass. Thus, highly muscular dogs, such as sighthounds, have higher baseline creatinine concentrations than other breeds.