ObjectiveOur objective is to identify the potential factors associated with serum Diacron’s reactive oxygen metabolites test (D-ROM) levels of patients with type 2 diabetes mellitus (T2DM) by conducting cross-sectional and longitudinal analyses in two large cohorts and further strengthening these results by performing a meta-analysis.MethodsSerum D-ROM concentrations were measured in 1045 and 1101 patients with T2DM from two independent cohort studies from Germany at baseline and repeatedly 3–4 years later. The cross-sectional and longitudinal associations of various potential determinants with D-ROM levels were assessed with a backwards selection algorithm in multivariable adjusted models.ResultsIn the meta-analysis of the cross-sectional analysis, female sex, low education, obesity, smoking, high total cholesterol, hemoglobin A1c ≥7%, no diabetes medication, a history of myocardial infarction, heart failure, a history of cancer and C reactive protein levels (CRP) >3 mg/L were statistically significantly associated with increased D-ROM levels in patients with T2DM. The meta-analysis of the longitudinal analysis revealed that old age, female sex, obesity, smoking, physical inactivity, high alcohol consumption, ≥5 years since diabetes diagnosis and CRP levels between 3 mg/L and 10 mg/L were statistically significantly associated with D-ROM levels measured 3–4 years later.Conclusions (validity, limitations and clinical applicability)This comprehensive analysis confirmed that several modifiable risk factors are being associated with oxidative stress in patients with T2DM within an observational study design. We discuss potential prevention measures against these risk factors that might help to reduce oxidative stress and to prevent some cases of premature mortality in patients with T2DM.