SIDE EFFECTS: Nausea, vomiting, diarrhea, loss of appetite, mouth sores, black hairy tongue, sore throat, dizziness, headache, or rectal discomfort may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: nail discoloration, muscle pain, difficult or painful swallowing, signs of kidney problems (such as change in the amount of urine), brown/gray tooth discoloration, numbness/tingling of the hands/feet, unusual fatigue, new signs of infection (e.g., persistent sore throat, fever, chills), hearing changes (e.g., ringing in the ears, decreased hearing), easy bruising/bleeding, severe stomach/abdominal pain, yellowing eyes/skin, dark urine. Tetracycline may rarely cause a serious increase in pressure inside the skull (intracranial hypertension-IH). The risk of this side effect is greater for women of childbearing age who are overweight or who have had IH in the past. If IH develops, it usually goes away after tetracycline is stopped; however, there is a chance of permanent vision loss or blindness. Get medical help right away if you have: persistent/severe headache, vision changes (such as blurred/double vision, decreased vision, sudden blindness), persistent nausea/vomiting. This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped.. Do not use anti-diarrhea or opioid medications if you have the following symptoms because these products may make them worse. Tell your doctor right away if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.. Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection (oral or vaginal fungal infection). Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge or other new symptoms. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, skin lesions/sores, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, new or worsening swelling/pain in the joints, chest pain, fast/irregular heartbeat. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: See also Side Effects section. Before taking tetracycline, tell your doctor or pharmacist if you are allergic to it; or to other tetracyclines (e.g., doxycycline, minocycline), or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, liver disease, problems swallowing, esophagus problems (e.g., hiatal hernia, reflux disease-GERD). This drug may make you dizzy. Alcohol or marijuana can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana. Tetracycline may cause live bacterial vaccines (such as typhoid vaccine) to not work as well. Do not have any immunizations/vaccinations while using this medication unless your doctor tells you to. This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness. Before having surgery, tell your doctor or dentist that you are using tetracycline. Caution is advised when using this drug in the elderly because they may be more sensitive to its effects. This medication should not be used in children younger than 8 years of age because it may cause permanent tooth discoloration and other problems. Tooth discoloration has also occurred in older children and young adults. Consult your doctor for more information. This medication is not recommended for use during pregnancy. It may harm an unborn baby. Consult your doctor for more details. This medication passes into breast milk in very small amounts. While there have been no reports of harm to nursing infants, consult your doctor before breast-feeding.

DRUG INTERACTIONS: See also How to Use. Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug include: atovaquone, retinoid medications taken by mouth (such as acitretin, isotretinoin), strontium, digoxin, kaolin pectin, warfarin. Although most antibiotics (including tetracycline) are unlikely to affect hormonal birth control such as pills, patch, or ring, a few antibiotics (such as rifampin, rifabutin) can decrease their effectiveness. This could result in pregnancy. If you use hormonal birth control, ask your doctor or pharmacist for more details. This product can affect the results of certain lab tests. Make sure laboratory personnel and your doctors know you use this drug.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.