Donating 400ml of blood has an impact on the human body because the total blood volume of the human body is about 7%-8% of the body weight. For an adult weighing 65kg, the total blood volume of the body is about 4000ml. Donating 400ml of blood, losing 1/10th of the body’s blood, will have a significant impact on the human body. After donating blood, most people will experience slight weakness, and in severe cases, they may experience pallor, dizziness and other discomforts. Therefore, after blood donation, take a good rest and replenish your nutrition. You need to take iron-rich foods such as pig’s blood, lamb’s blood and purple cabbage. You should also eat high quality protein, such as fresh milk, soybeans, meat, fish, etc. You should also eat more fresh fruits and vegetables, such as bananas, oranges, apples, etc. Usually after a week or so of rest, the amount of hemoglobin will gradually return to normal, and the strength will gradually return to normal.