What are the side effects of an 800 milligram dose of ibuprofen?

Possible side effects of an 800 milligram dose of ibuprofen include stomach upset accompanied by vomiting, diarrhea or constipation, lethargy, and headaches, states WebMD. More serious side effects are also possible but unlikely to occur. Heavy or long-term use can result in liver damage in rare instances.

Consult a doctor if the aforementioned side effects grow in duration or severity or in the event of more urgent side effects, recommends Drugs.com. Rare and more serious side effects include swelling of extremities, stiffness in neck, a propensity to bleed or bruise, extreme lethargy, unusual weight gain, and changes in hearing or vision. Seek immediate medical attention at the onset of symptoms of liver damage, such as jaundice, severe abdominal pain and dark urine.