Complete fasting requires a fasting time of more than 6 hours, which mostly refers to taking the drug on an empty stomach early in the morning, but the usual term for taking a drug on an empty stomach generally refers to 1 hour before and 2 hours after a meal. Some drugs are taken before or after meals based on the purpose of the drug and the nature of the drug (acidity and alkalinity) to decide. For example, insulin stimulants for diabetes need to be taken about 15 minutes before a meal. Enteric aspirin is taken on an empty stomach because the acidic drug is stable and does not disintegrate in an acidic environment to avoid irritation of the stomach. Some are fat-soluble or water-soluble factors that affect the absorption of the drug. Related to the characteristics of the food eaten, can affect the absorption effect of the drug and the absorption time. Such as the drug rehabilitation new liquid for repairing gastric mucosa and the drug Xinonar for increasing gastric power, these drugs are not too stimulating to the stomach and intestines, and usually need to be taken on an empty stomach before meals. After the meal, stomach acid is reduced, alkaline drugs are not easy to disintegrate. So the drug is fasting or after meals to eat must have instructions clearly required or doctor’s guidance, so as not to affect the effectiveness of the drug or adverse reactions.