Vitamin D and Type 2 Diabetes Study (D2d Study)

The purpose of this study is to evaluate the effect of taking vitamin D supplements on the prevention of diabetes in people who are at high risk for diabetes. D2d is a multi-center trial, and will consist of a total of approximately 2,400 participants nationwide. Please feel free to check the study website for more information. 

Eligible Participants

Eligible participants for this study meet the following criteria:

  • Both men and women
  • 30 years of age or older
  • Have prediabetes (“borderline” diabetes)
  • Must be willing to be randomly assigned to take either a vitamin D supplement (4000 international units) or a placebo for roughly 4 years

Study Design

Participation in the study will require up to 13 scheduled visits to the Clinical Translational Unit (CTRU) at Stanford Hospital & Clinics, which will include blood draws at certain time points.

Depending on study involvement, participants may receive up to $320 in compensation over 4 years.

How to Participate

If you are interested in participating, please contact the study coordinator, Melanie Rosenberg, at or 650-485-3910.