GCK‐MODY patients had lower HbA1c compared to HNF1A‐MODY patients (SMD −1.12 [95% CI −1.64, −0.60] %, p < .001, n = 18; I2 = 94%, Ph <.01), irrespective of patient type, and in type 2 diabetes studies, the difference was only significant for subgroups that contained all family members (overall SMD −1.54 [95% CI −2.88, −0.19] %, p = .03, n = 13; I2 = 99%, Ph <.01). This evidence concerns the gene HNF1A and type 2 diabetes mellitus.