DNMT3A and type 2 diabetes mellitus: We next wanted to ascertain the prevalence of DNMT3A-R882-mutant CH and other CH subtypes among diagnosed diabetics who had not been on metformin at any time before recruitment, but we could not confidently identify these in the UKB, particularly as 90% of individuals diagnosed with T2D in the UK at that time were treated initially with metformin39.