The most common side effect is heaviness of stomach. Headache, abdominal pain, nausea, constipation, vomiting, flatulence or diarrhea may also appear. These symptoms are usually mild and disappear within a few days without interrupting treatment. By taking Grendis with meals, the possibility of GI effects decreases. Occasionally, GI bleeding, blood in urine, bruising, nose bleeds, gum bleeds or cerebral hemorrhage have been observed. There have also been some isolated cases of photosensitivity.