In the sensitivity analysis according to the Hardy-Weinberg equilibrium (HWE), the results were consistent with those in non-sensitivity analysis. However, in the sensitivity analysis according to the control source from hospital, sample size of case (100), sample size of case (5100), the MTHFR A1298C gene polymorphism was not associated with T2DN risk. In conclusion, the MTHFR A1298C gene polymorphism was not associated with T2DN risk. However, additional studies are required to firmly establish a correlation between the MTHFR A1298C gene polymorphism and T2DN risk.