I have been on Lithium Carbonate (1800 mg/day) for over 4 years. Lived with diarrhea, acne, tremors, etc. throughout, but otherwise loved the drug. After filling toilet with blood several times last week, I went into the hospital. Colonoscopy & endoscoopy revealed severe diverticulosis and severe Barrett's esophagus, respectively. All involved are shaking their heads, as these tests were relatively normal 3 years ago. I suspect Lithium.