doxycycline monohydrate 100 mg tablet is a medication belonging to the tetracycline class of antibiotics. It is used to treat a wide range of bacterial infections, including respiratory tract infections, skin infections, urinary tract infections, and various sexually transmitted diseases. Doxycycline works by inhibiting the growth and spread of bacteria in the body, ultimately helping the immune system to eliminate the infection. It is available in various forms, including capsules, tablets, and suspensions. Patients should take it as directed by a healthcare provider and complete the full prescribed course, even if their symptoms improve, to ensure the infection is fully treated and prevent antibiotic resistance.