Sarcopenia is a progressive geriatric syndrome defined by the loss of skeletal muscle mass and function, affecting approximately 10% of adults aged 60 and above. Its prevalence varies substantially depending on the living setting, demographic characteristics, measurement tools and diagnostic criteria applied. Several international working groups, including the EWGSOP, AWGS, IWGS, FNIH and SDOC, have proposed distinct definitions and cut-off values, contributing to significant heterogeneity in reported prevalence rates. This video critically evaluates the most widely used diagnostic criteria and measurement techniques for sarcopenia, including screening tools such as SARC-F and SARC-CalF, body composition assessment methods (DXA, BIA, CT, MRI), muscle strength tests and physical performance batteries. The role of emerging biomarkers and genetic factors is also discussed. The aim is to support clinicians and researchers in selecting the most appropriate diagnostic approach based on study objectives, population characteristics and available resources.