This post-market clinical follow-up (PMCF) investigation evaluates the accuracy and safety of two CE-marked continuous glucose monitoring (CGM) systems, the Anytime 5Pro and the Anytime 4Pro, in adults with type 1 or type 2 diabetes. Each participant simultaneously wears one Anytime 5Pro sensor and one Anytime 4Pro sensor, one on each upper arm, for the full labelled wear period of each device (up to 16 and 15 days, respectively). CGM readings are compared against venous blood glucose measured by a laboratory reference analyzer (YSI 2500) during four in-clinic sampling sessions that include controlled glucose manipulation. Participants are masked to real-time CGM readings throughout the study. The investigation is conducted to confirm device performance and safety under real-world conditions of use in a European population, in line with the manufacturer's post-market clinical follow-up obligations under the EU Medical Device Regulation.