There is no single medicine that permanently regularizes periods, as treatment depends entirely on the underlying cause. Irregular cycles are typically due to hormonal imbalances, such as Polycystic Ovary Syndrome (PCOS), thyroid dysfunction, or chronic stress. Simply using pills to induce withdrawal bleeding only addresses the symptom, not the root issue. To achieve a long-term solution, please consult a gynecologist. They can perform a pelvic ultrasound and hormone blood tests to diagnose the cause. Treatment may involve targeted lifestyle modifications (diet and exercise), thyroid management, or specific hormonal therapy tailored to your body's needs.