Even though GFR is reduced in ageing and CKD, the magnitude of this reduction is the expected for age, with normal serum urea, creatinine, hematocrit, erythropoietin, parathyroid levels, as well as normal urinalyses and renal imaging in ageing, while at least one of these parameters is altered in CKD patients (Table 1) [3]. Here, EPO is linked to chronic kidney disease.