Doxycycline monohydrate 100 mg tablet are a type of antibiotic used to treat bacterial infections. They belong to the tetracycline class of antibiotics and work by inhibiting bacterial protein synthesis, thereby preventing the growth and spread of bacteria. Common uses include treating infections such as acne, urinary tract infections, respiratory infections, and certain sexually transmitted diseases. It is typically taken orally, often with food to reduce stomach upset, and should be used as directed by a healthcare provider. Side effects may include nausea, diarrhea, and sun sensitivity. Avoid taking with dairy products or antacids containing calcium, magnesium, or aluminum.