Background: Vitamin D might be beneficial in diabetic patients with ischemic heart disease through its favorable effect on metabolic profiles and biomarkers of inflammation and oxidative stress. We performed a protocol for systematic review and metaanalysis to assess whether vitamin D supplementation could improve glucose control and inflammation in type 2 diabetic patients with ischemic heart disease.Methods: The proposed systematic review and meta-analysis will conform to the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols. Seven electronic databases including Web of Science, Embase, PubMed, Wanfang Data, Scopus, Science Direct, Cochrane Library were searched in October 2022 by 2 independent reviewers. The risk of bias assessment of the included studies was assessed using the tool recommended in the Cochrane Handbook for Systematic Reviews of Interventions (version 5.1.0). Data analysis was performed with Review Manager Software (RevMan Version 5.4, The Cochrane Collaboration, Copenhagen, Denmark).Results: This study will provide a high-quality synthesis to assess the effectiveness and safety of vitamin D supplementation on type 2 diabetic patients with ischemic heart disease. Conclusion:This systematic review may lead to several recommendations, for both patients and researchers, as which is the best therapy for type 2 diabetic patients with ischemic heart disease and how future studies need to be designed, considering what is available now and what is the reality of the patient.Abbreviations: hs-CRP = high-sensitivity C-reactive protein, IHD = ischemic heart disease, T2DM = type 2 diabetes mellitus.