Diabetes is a growing health issue in Australia with the prevalence increased from 3.3% in 2001 to 4.9% in 2017-2018 where 86% of diabetes is type 2 diabetes. Metformin is the first-line pharmaceutical in treatment of type 2 diabetes and ranked at 8th of most prescribed pharmaceutical in Australia. With respect to high volume of prescription and almost 100% excreted unmodified, metformin have been detected ubiquitously in the aquatic environment. In this study, we developed and applied a sensitive and simple method using direct-injection LC-MS/MS for measurement metformin in wastewater influent. We showed that in sewer reactors, metformin was degraded 40% in gravity sewers in 12 hours and 90% in raising main in the same period. Wastewater from 69 wastewater treatment plants across Australia, covering 40% of the total population on the 2016 census day, were subsequently analysed. Metformin was detected in all wastewater sample with concentration ranging from 8.2 to 191.4 µg/L. National per capita metformin load released into wastewater was estimated 28.6 g/d/1000 people with total release 691 kg/day. In different states, metformin load was highest in wastewater in ACT (34.0 g/d/1000 people), followed by NSW (33.8 g/d/1000 people) and TAS (30.3 g/d/1000 people) and lowest in SA (19.2 g/d/1000 people) and NT (22.8 g/d/1000 people). Variation of metformin load in wastewater was also observed in different type of cities with major cities (29.0 g/d/1000 people) and inner regional cities (28.5 g/d/1000 people) showed higher level than the load in outer regional cities (18.8 g/d/1000 people) and remote cities (15.6 g/d/1000 people). To the best of our knowledge, this was the first national study to reveal a spatial distribution of metformin in Australian wastewater.