Introduction: In November 2020, the FDA approved a novel colonoscopy preparation, a tablet-based bowel prep containing poorly absorbed sulfate salts. This case series includes 3 patients undergoing upper and lower endoscopy who were found to have gastric irritation thought to be caused by this bowel preparation. Case Description/Methods: A 35-year-old male with gastroesophageal reflux presented with 5-day history of hematochezia and abdominal pain. He underwent colonoscopy which showed internal hemorrhoids and esophogastroduodenoscopy (EGD) showed ulceration of the stomach body (Figure, top left). Biopsies showed focal active gastritis and superficial erosion without H. pylori organisms. The patient started daily PPI and 3 months later repeat EGD showed normal mucosa both visually and pathologically. A 59-year-old female endorsed abdominal bloating and heartburn after completing treatment for H. pylori 1-month prior. She underwent EGD with colonoscopy (for screening). EGD showed multiple diminutive round erythematous spots in the stomach antrum with pinpoint foci of dark heme suggestive of hemorrhagic gastritis (Figure, top right). Biopsies showed moderate inactive chronic inflammation without H. pylori organisms. A 70-year-old female requested endoscopy as she had a personal history of remote H. pylori infection and her father had gastric cancer. On EGD, there were superficial erosions in the lesser curve of the stomach (Figure, bottom 3). Biopsies were obtained and showed gastric mucosa with reactive epithelial changes without evidence of H. pylori infection. Discussion: The preparation consists of 24 tablets total, each taken with 16 ounces of water. The ingredients include magnesium sulfate, potassium chloride, and sodium sulfate. The sulfate salts are responsible for the osmotic and therefore laxative effects of the medication. Potassium chloride is included to avoid diarrhea induced hypokalemia. Potassium chloride is a mucosal irritant that has been reported to cause upper gastrointestinal ulcers and erosions. In each case, gastric irritation was an unexpected finding in a patient without significant risk factors for developing gastric ulcers. The common factor among them all is the same tablet-based preparation used for colonoscopy. Noted was a similar pattern of ulceration in the gastric antrum and body noted in these patients, which was in a pattern of the tablets resting on the greater curve of the stomach. While gastric ulceration may be asymptomatic, it may lead to diagnostic confusion and further unnecessary workup.Figure 1.: Colonoscopy images.