More common side effects of tetracycline may include: Anemia, blood disorders, blurred vision and headache (in adults), bulging soft spot on the head (in infants), diarrhea, difficult or painful swallowing, dizziness, extreme allergic reactions, genital or anal sores or rash, hives, inflammation of large bowel, inflammation of the tongue, inflammation of the upper digestive tract, increased sensitivity to light, loss of appetite, nausea, rash, ringing in the ears, swelling due to fluid accumulation, vision disturbance, and vomiting. Less common or rare side effects may include: Inflamed skin, inflammation of the penis, liver poisoning, muscle weakness, peeling, skin eruptions, and throat sores and inflammation.

Do not take tetracycline if you are sensitive to or have ever had an allergic reaction to any tetracycline medication. If you have kidney disease, make sure the doctor knows about it, as a lower than usual dose of tetracycline may be needed. Tetracycline drugs can make you more prone to sunburn when you are in sunlight or ultraviolet light. Take appropriate precautions. As with other antibiotics, use of this medication may cause other infections to develop. Contact your doctor if this occurs. Tetracycline is not recommended for use during pregnancy, as it can affect the development of the unborn child's bones and teeth. If you are pregnant or plan to become pregnant, inform your doctor immediately. Tetracycline appears in breast milk and may affect a nursing infant.

If you miss a dose of tetracycline, take it as soon as you remember. If it is almost time for your next dose and you take tetracycline once a day (e.g., for acne), take the dose you missed, and then take the next one 10 to 12 hours later; if you take it twice a day, take the dose you missed, and then take the next one 5 to 6 hours later; if you take 3 or more doses a day, take the one you missed, and then take the next one 2 to 4 hours later. Then resume your regular schedule.