You can eat before donating blood, but there are clear requirements on the type and time of eating. Light, liquid, easily digestible food such as thin porridge, noodles, rice flour, green vegetables, steamed buns, oatmeal, broccoli, etc. can be eaten before blood donation, preferably two hours before donation. Foods that can be eaten half an hour before the patient donates blood include cookies and drinks with high sugar content. The main concern is that after the patient donates blood, there will be a lack of energy due to blood loss and the patient will experience dizziness, coma and other uncomfortable symptoms. The foods that cannot be eaten before blood donation are mainly greasy, spicy, stimulating and hard to digest foods, including alcohol, red meat, roast chicken, roast duck and pig’s feet. These foods will cause the patient’s blood lipid viscosity to rise, causing liver function damage and making the patient’s blood unable to meet the blood donation standards.