Tetracycline is a prescription medicine that can be used to treat a wide range of infections caused by bacteria. Tetracycline works by preventing further growth of bacteria. Your doctor needs to know if you are using oral contraceptives, anticoagulants, antacids, herbal products, penicillin, vitamins, or nutritional supplements, as drug interactions are possible. Tetracycline has been reported to decrease the efficiency of oral contraceptives. This can be dangerous as this medicine has been classified as FDA pregnancy category D. Tetracycline can cause dangerous health effects in nursing and unborn babies. This drug is usually well tolerated, but serious side effects are still possible. Make sure you tell your doctor if you get any of the following serious side effects: blurred vision, loss of appetite, severe blistering, jaundice, severe pain in your upper stomach, fever, chills, urinating less than usual, dizziness, severe headache, confusion or weakness, dark colored urine, easy bruising or bleeding, body aches, and red skin rash. Such side effects as changes in skin color, redness of the skin, itching of the rectum, sore mouth, upset stomach, and diarrhea are considered to be mild and there is no need to contact your health care provide about them.