Doxycycline monohydrate 100 mg is a broad-spectrum antibiotic belonging to the tetracycline class, widely used to treat bacterial infections such as acne, respiratory infections, Lyme disease, and sexually transmitted diseases. It works by inhibiting the production of proteins that bacteria need to grow and multiply, effectively stopping the spread of infection. Doxycycline is available in tablet, capsule, and liquid forms, and is also used as a preventive measure against malaria. It’s typically taken once or twice daily, with or without food, though dairy products may reduce its absorption. Always follow your doctor’s instructions for safe and effective use.