What are the side effects of guarana?

What are the possible side effects of guarana ()? Although rare, serious side effects from guarana have been reported. Stop taking guarana and seek emergency medical attention if you experience
  • a serious allergic reaction including difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives; or
  • irregular heartbeats or chest pain.
Other less serious side effects may also reported with the use of guarana. Talk to your doctor or health care provider if you experience
  • heartburn;
  • upset stomach;
  • loss of appetite;
  • constipation or diarrhea;
  • nervousness, irritability, or anxiety;
  • sleeplessness;
  • irregular heartbeats; or
  • headache.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.