Professional flash continuous glucose monitoring using the FreeStyle Libre ProTM system is recently available in the U.S. This is one of the first real-world studies evaluating glucose metrics of sequential monitoring periods using a cross-sectional observational design. Between September 2016 and January 2018, de-identified data from 2,836 users having 2 sequential sensors (at least 5 days each) were divided by the 1st sensor above and below an estimated A1c (eA1c) of 7.5%. Glucose metrics for the two sensors were compared. For those starting above an eA1c of 7.5%, the eA1c reduced from 9.6% to 8.7% (-0.9%, p<0.001), and time in range (70-180 mg/dL) increased from 7.8 to 10.5 h/day (2.7 h/day, p<0.001). Time above 180 mg/dL decreased from 15.7 to 12.5 h/day (-3.2 h/day, p<0.001), while hypoglycemia below 70 mg/dL increased but stayed below 5.0% (29 to 59 minutes/day, 30.1 minutes/day change, p<0.001). For those at an eA1c of 7.5% or lower, eA1c increased but stayed in target (6.4% to 6.9%, 0.5% change, p<0.001), while time below 70 mg/dL reduced by 22%, from 115 to 91 minutes/day (-24.8 minutes/day, p<0.001). Professional glucose monitoring in clinical practice aids in the reduction of hyperglycemia and increased time in range while maintaining minimal hypoglycemia for those with average levels above target. Those with average levels in target benefit by reduced exposure to hypoglycemia.