It is not safe to take ibuprofen on an empty stomach, as this may irritate the stomach lining and cause bleeding, states Cancer Research UK. As of 2015, common side effects of ibuprofen affect more than 10 in 100 individuals and may include heartburn, indigestion and stomach ache.
Occasional side effects are bloody stools, headaches, loss of appetite, a sensation of sickness and itchy rash, according to Cancer Research UK. High blood pressure, kidney changes and liver changes are rarer and more serious side effects. Women who are in their final trimester of pregnancy should not take ibuprofen because of a risk of birth defects. Those who are within their first six months of pregnancy should first consult a doctor if planning to take ibuprofen.