Background: Melasma is pale brown to dark brown hyperpigmentation of the facial skin that commonly affects women of reproductive age. Treatment methods for melasma include oral and topical use of vitamin C, hydroquinone ointment, and laser treatment, with unsatisfactory results. Tranexamic acid (TA) has been shown to be effective against melasma, however, the optimal dose has not been investigated. Objective: To analyse the therapeutic effect of different doses of oral TA on melasma. Materials & Methods: Patients with severe melasma were randomised to receive TA at a daily dose of 500 mg, 750 mg, 1,000 mg, or 1,500 mg. Clinical and VISTA photographs of the patients were taken at baseline, four weeks, eight weeks, six months, one year, and two years. The melasma area and severity index (MASI), as well as the melanin index, were measured. Routine blood and coagulation tests were performed at each time point. The photographs were divided into five groups according to level of improvement: apparent improvement, slight improvement, unchanged, and deterioration. Results: Clinical photographs showed that all four doses of TA were effective in treating melasma, and the efficacy correlated with treatment time and dosage. However, there were no significant differences in the MASI or melanin index between the four doses. The treatment was generally safe for most patients and side effects included mild stomach upset and decreased menstruation. Conclusion: Oral TA was safe and effective for the treatment of melasma. Patient satisfaction was high and most patients could withstand long-term treatment.