-In HOMA calculations in combination with glucose (e.g. HOMA-B).-To differentiate T1D versus T2D (especially in newly diagnosed, insulin-naïve patients)-To assess β-cell function in T2D (before escalating to insulin, to assess response to therapies over time-Screening for LADA (paired with autoantibodies). The gene discussed is INS; the disease is type 1 diabetes mellitus.