The main objective of this proposal is to pilot a two-arm randomized controlled trial comparing these two doses. The participants are infants from the general population identified at increased genetic risk for type 1 diabetes by cord blood or filter paper blood spot HLA class II genetic screening. The study will measure key safety, compliance and pharmacokinetic, surrogate efficacy, and process outcomes including growth parameters, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels, calcium levels in blood and urine, bone mineral content and body composition by densitometry, diabetes-related autoantibodies markers for beta-cell autoimmunity, and recruitment rates for both the screening and for the intervention trial.