The following are contraindications to the use of vitamin C tablets: 1. Patients with digestive and malabsorption problems and upper gastrointestinal bleeding, patients with obvious previous gastric ulcers, duodenal bulb ulcers and a past history of upper gastrointestinal bleeding, are contraindicated during the active phase of peptic ulcers. Patients with a history of upper gastrointestinal bleeding are absolutely contraindicated. 2. Patients with esophagogastric varices, cirrhosis, and portal hypertension are also contraindicated for vitamin C tablets. 3. Patients with acute renal failure and liver failure are contraindicated for vitamin C tablets because such patients cannot 4. Patients with widespread disseminated intravascular coagulation, such as DIC, are also contraindicated for vitamin C tablets.