Before taking tetracycline,

• tell your doctor and pharmacist if you are allergic to tetracycline, minocycline, doxycycline, sulfites, or any other medications.
• tell your doctor and pharmacist what prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take, especially antacids, anticoagulants ('blood thinners') such as warfarin (Coumadin), and penicillin. Tetracycline may decrease the effectiveness of some oral contraceptives; another method of birth control should be used while taking this drug.
• be aware that antacids, calcium supplements, iron products, and laxatives containing magnesium interfere with tetracycline, making it less effective. Take tetracycline 1 hour before or 2 hours after antacids (including sodium bicarbonate), calcium supplements, and laxatives containing magnesium. Take tetracycline 2 hours before or 3 hours after iron preparations and vitamin products that contain iron.
• tell your doctor if you have or have ever had diabetes, allergies, asthma, hay fever, hives, or kidney or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking tetracycline, call your doctor immediately. Tetracycline can harm the fetus.
• if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking tetracycline.
• plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Tetracycline may make your skin sensitive to sunlight.
• you should know that when tetracycline is used during pregnancy or in babies or children up to age 8, it can cause the teeth to become permanently stained. Tetracycline should not be used in children under age 8 unless your doctor decides it is needed.

Tetracycline may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• upset stomach
• diarrhea
• itching of the rectum or vagina
• sore mouth
• redness of the skin (sunburn)
• changes in skin color

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:

• severe headache
• blurred vision
• skin rash
• hives
• difficulty breathing or swallowing
• yellowing of the skin or eyes
• itching
• dark-colored urine
• light-colored bowel movements
• loss of appetite
• upset stomach
• vomiting
• stomach pain
• extreme tiredness or weakness
• confusion
• joint stiffness or swelling
• unusual bleeding or bruising
• decreased urination
• pain or discomfort in the mouth
• throat sores
• fever or chills