Almost all laboratories in The Netherlands report an estimated glomerular filtration rate (eGFR) whenever a value for plasma creatinine is requested. This formula is based on gender and age, besides the plasma creatinine concentration, and sometimes also a correction for race is applied. While this GFR reporting improved the recognition of chronic kidney disease, the formulas used have intrinsic limitations. Moreover, recently a novel formula that obviates the need for a correction factor for race has been proposed. In this article the strengths and weaknesses of plasma creatinine and formulas based on that are discussed, following ten frequently asked questions.