Normally, abstinence is not necessary after donating 400ml of blood. Blood donation of 400ml represents 10% of the total blood volume of the body. The stored blood will be replenished quickly after donation and will not reduce the circulating blood volume. Specifically, the water and inorganic substances lost after blood donation will be replenished within 1-2 hours; the plasma protein synthesized by the liver will be replenished within only 1-2 days; and platelets, white blood cells and red blood cells will be quickly restored to their original levels. Therefore, donating 400ml of blood will not have any special effects on the body and no abstinence is needed. However, care needs to be taken to protect the venipuncture site after blood donation. Do not moisten the needle opening with water for 24 hours and avoid pressing and rubbing. Patients should not engage in activities such as working at height, high temperature work, driving vehicles, sports competitions or overnight entertainment on the day after blood donation, and avoid staying up late. In addition, patients can eat fresh vegetables and fruits, soy products, dairy products, fresh fish, shrimp, meat and eggs in moderation.