Diarrhea, nausea, or vomiting may occur. If any of these effects persist or worsen, tell the doctor or pharmacist promptly. Taking this medication with food will help to reduce stomach upset.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 the doctor right away if any of these rare but serious side effects occur: dark urine, persistent nausea/vomiting, severe stomach/abdominal pain, yellowing eyes/skin, easy bruising/bleeding, new signs of infection (such as fever, persistent sore throat), unusual tiredness.This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a type of resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have any of the following symptoms because these products may make them worse. Tell the 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. Contact the 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, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.Amoxicillin can commonly cause a mild rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe allergic reaction. Therefore, get medical help right away if you develop any rash.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.