Methyclothiazide is primarily used as a diuretic to treat high blood pressure and fluid retention caused by various medical conditions, such as heart failure, kidney disorders, or liver disease. It works by helping the kidneys eliminate excess salt and water from the body, which reduces swelling and lowers blood pressure. This medication is often prescribed as part of a comprehensive treatment plan that may include dietary changes, exercise, and other medications. It is important to follow the prescribed dosage and monitor for potential side effects, such as electrolyte imbalances or dizziness. Regular medical check-ups are recommended to ensure its effectiveness and safety.