There is no consensus on treatment of leukoplakia but surgical excision is the preferred choice if suitable in size, which does not prevent clinical recurrence and malignant transformation. Chemoprevention is a new direction in the management of OL using various topical and systemic agents such as; vitamin A, lycopene, celecoxib, green tea extract, and metformin. While metformin cannot realistically be used as cancer mono-therapy, it can be used as an adjunct and can have a more promising effect on lesions that have yet to undergo malignant transformation. Thus, the aim of this study is to investigate the efficacy of combined chemo-preventive effect of topical and systemic Metformin on oral leukoplakia.