Vitamin C is best taken at a dose of one capsule a day, usually about half an hour after breakfast. Vitamin C has strong antioxidant properties and is a water-soluble vitamin that can help improve cold symptoms and shorten the duration of the cold, and can regulate the internal environment of the body, promote the use of calcium, iron and folic acid, and improve immunity. Vitamin C is generally recommended to be taken about half an hour after breakfast, when the gastrointestinal function is active, which is conducive to full absorption and utilization, and can reduce the stimulation of the gastrointestinal tract. Vitamin C should not be taken on an empty stomach to prevent rapid absorption into the blood and rapid excretion through the urine. It is best to apply vitamin C under the guidance of a doctor, not to blindly stop or increase the dosage on your own. Usually, you can also eat more vitamin C rich vegetables and fruits instead of taking medicine. Secondly, peptic ulcers should be used with caution to avoid stimulating the ulcer surface, leading to ulcer deterioration, bleeding or perforation.