Doxycycline monohydrate 100 mg tablet is effective against a wide range of bacterial infections, including respiratory infections, urinary tract infections, sexually transmitted infections like chlamydia and gonorrhea, as well as certain skin infections and tick-borne illnesses like Lyme disease. However, it does not treat viral infections such as flu or common colds. The effectiveness of Buy doxycycline online can vary depending on the specific bacteria causing the infection and its susceptibility to the antibiotic. It's crucial to take the full course of treatment as prescribed by a healthcare provider to ensure the infection is completely eradicated and to minimize the risk of antibiotic resistance.