The best time to donate blood is when the body is in the best condition, and you should not be sick or take oral medication, including oral antibiotics and cold medication, for a month. In addition, you should not stay up late in the days before blood donation to avoid damage to liver function. When donating blood, you can start with 200ml of blood depending on your health condition. If you feel well enough, you can donate 400 ml of blood, and you should rest afterwards and take milk, protein and water supplements. If you experience dizziness, nausea, vomiting or other symptoms, you should seek treatment in a timely manner and go to the hospital if necessary. If there is no discomfort after donating blood, the next blood donation is recommended three months later.