Most routine tests used to diagnose CKD do not identify abnormal findings until there is advanced disease (stage 2 or higher). Currently, the most common way to diagnose CKD is by first detecting evidence of changes in renal function (e.g., azotemia, proteinuria) that arise as a result of renal lesions (Lees, 2004). Looking for subtle changes (e.g., gradually increasing serum creatinine over time, progressive decline in urine concentrating ability or presence of mild proteinuria) is helpful for identifying CKD at earlier stages. (Lees, 2004) Symmetric dimethylated arginine (SDMA) has recently become available in the veterinary marketplace as a reliable, early surrogate marker of GFR and, like creatinine, its reciprocal has a linear relationship with GFR (Braff et al, 2014). It has been shown to be an earlier marker of kidney dysfunction than creatinine in both dogs and cats (Hall et al, 2014, Nabity et al, 2015, Yerramilli et al, 2014, Yerramilli et al, 2016). Importantly SDMA does not appear to be affected by extra-renal factors, importantly lean body mass, making it a more sensitive marker for kidney disease than serum creatinine in patients with muscle loss (Hall et al, 2014, Hall et al, 2015, Relford et al, 2016). Both IRIS and ISFM guidelines for diagnosis and management of CKD recommend incorporating SDMA for early detection of kidney disease in dogs and cats (Sparkes et al, 2016, IRIS Staging of CKD). Persistent increases in SDMA greater than 14 mg/dL suggest reduced kidney function and the possibility of IRIS CKD stage 1 in patients with serum creatinine level less than the IRIS cutoff of 1.4 mg/ dL for dogs and 1.6 mg/dL for cats. SDMA can help to identify dogs and cats in IRIS stage 1 and early IRIS stage 2 in which clinical signs are absent or mild and serum creatinine level is not above the reference interval. Most animals with early kidney disease have an SDMA level between 15 and 20 mg/dL. Because SDMA level increases as kidney function decreases, SDMA levels greater than 20 mg/dL are typically seen in more advanced disease along with an increased serum creatinine level. A complete urinalysis should be performed to evaluate for inappropriate specific gravity, proteinuria, and other evidence of kidney disease. Making an early diagnosis of CKD generally requires finding 1 or more of the following: serum creatinine level increasing within the reference range, persistently increased SDMA, abnormal kidney imaging or persistent renal proteinuria (weeks to months). Earlier diagnosis of CKD allows for investigation for underlying causes and earlier therapeutic intervention, which could slow or halt disease progression.