Vancomycin is an antibiotic used to treat a number of bacterial infections. It is recommended intravenously as a first-line treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, and meningitis caused by methicillin-resistant S. aureus. Blood levels may be measured to determine the correct dose. Vancomycin is also recommended by mouth as a treatment for severe Clostridium difficile colitis. When taken by mouth it is very poorly absorbed.