To cite QDiabetes in publications use:

  Benjamin G. Feakins, Sarah L. Lay-Flurrie, Richard J. Stevens, Trish
  Greenhalgh, Tim A. Holt, Evangelos Kontopantelis, Dianna M. Smith and
  Bernard C. Gudgin (2021). QDiabetes: A package to calculate risk of
  type 2 diabetes. R package version 1.0-2,
  https://cran.r-project.org/package=QDiabetes

A BibTeX entry for LaTeX users is

  @Manual{QDiabetes-package,
    title = {{QDiabetes}: A package to calculate risk of type 2 diabetes},
    author = {Benjamin G. Feakins and Sarah L. Lay-Flurrie and Richard J. Stevens and Trish Greenhalgh and Tim A. Holt and Evangelos Kontopantelis and Dianna M. Smith and Bernard C. Gudgin},
    year = {2021},
    note = {R package version 1.0-2},
    url = {https://cran.r-project.org/package=QDiabetes},
  }