There is no specific size to determine the severity of a duodenal ulcer. However, ulcers with a diameter greater than 1.5 cm are generally considered large. In such cases, strong acid-suppressing medications are needed for treatment, along with drugs to protect the gastric mucosa. Additionally, it is necessary to test for Helicobacter pylori infection. If the infection is positive, a bismuth-containing quadruple therapy should be used for two weeks to eradicate Helicobacter pylori. The choice of specific medications, as well as their dosages and administration, should be under the guidance of a doctor.