Stomach upset, nausea, vomiting, loss of appetite, headache, dizziness, or unusual tiredness may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.This medication may cause your skin and urine to turn orange-yellow. This effect is harmless and will disappear when the medication is stopped.Rarely, delayed-release tablets of sulfasalazine may appear whole or only partly dissolved in your stool. If this occurs, tell your doctor immediately so your treatment can be changed.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.This medication may cause temporary male infertility. This effect is reversible when the medication is stopped.Tell your doctor right away if you have any serious side effects, including: sun sensitivity, hearing changes (e.g., ringing in the ears), mental/mood changes, painful urination, blood in the urine, change in the amount of urine, new lump/growth in the neck (goiter), numbness/tingling of the hands/feet, signs of low blood sugar (e.g., hunger, cold sweat, blurred vision, weakness, fast heartbeat), swollen glands.This medication may rarely cause very serious allergic reactions (e.g., Stevens-Johnson syndrome), blood disorders (e.g., agranulocytosis, aplastic anemia), liver damage, nerve/muscle problems and infections. Get medical help right away if you have any very serious side effects, including: skin rash/blisters/peeling, mouth sores, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing, chest pain, signs of infection (such as fever, chills, persistent sore throat, cough), easy bruising/bleeding, severe tiredness, muscle pain/weakness (especially with fever and unusual tiredness), pale or blue skin/lips/nails, new/worsening joint pain, confusion, persistent/severe headache, unexplained neck stiffness, seizures, signs of liver problems (e.g., persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin, dark urine).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.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.