Chronic kidney disease (CKD) is a frequent affection, most often detected by evaluation of the glomerular filtration rate (GFR). Measuring GFR by a reference method is not possible for every single patient, even if these methods are probably underused. However, serum creatinine has several limitations of which clinicians should be aware. Knowing these limitations, creatinine and creatinine-based equations (including other parameters like age, gender and ethnicity) still represent the most used and easiest way to detect and assess CKD.