We did not consider glucagon-like peptide-1 receptor agonists because this class was rarely prescribed as a second line antidiabetic treatment in the UK during the study period,12, 13 and they are still not recommended as second line treatment for people with type 2 diabetes mellitus.12 The prescribing of glucagon-like peptide-1 receptor agonists is increasing in the US, however, and warrants further study as the number of people prescribed these drugs increases in routinely collected data. This evidence concerns the gene GLP1R and type 2 diabetes mellitus.