Why is this medication prescribed? Cephalexin is a cephalosporin antibiotic used to treat certain infections caused by bacteria such as pneumonia and bone, ear, skin, and urinary tract infections. Antibiotics will not work for colds, flu, or other viral infections. This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information. How should this medicine be used? Cephalexin comes as a capsule, tablet, and liquid to take by mouth. It is usually taken every 6 hours (four times a day) or every 12 hours (twice a day) for 7-10 days. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take cephalexin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Shake the liquid well before each use to mix the medication evenly. The capsules and tablets should be swallowed whole and taken with a full glass of water. Continue to take cephalexin even if you feel well. Do not stop taking cephalexin without talking to your doctor. What special precautions should I follow? Before taking cephalexin, tell your doctor and pharmacist if you are allergic to cephalexin or any other cephalosporin antibiotic such as cefadroxil (Duricef) or cephradine (Velosef), penicillin, or any other drugs. tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially other antibiotics, anticoagulants ('blood thinners') such as warfarin (Coumadin), probenecid (Benemid), and vitamins. tell your doctor if you have or have ever had kidney or liver disease, colitis, or stomach problems. tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking cephalexin, call your doctor. if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking cephalexin.