It is generally not harmful for girls to donate blood when they meet the conditions for blood donation, but if they do not meet the requirements for blood donation or if the medical personnel make mistakes in operation, it may cause anemia, infection and other hazards. 1. Anemia: The blood donation regulations in various regions of China generally stipulate that the age of the donor should be between 18 and 55 years old, and the weight of the girl should be more than 45kg. In addition, for girls, those whose hemoglobin is lower than 115g/L, and those who are on their physiological period and the three days before and after are not allowed to donate blood. If girls do not meet the above conditions or donate too much blood, they are very likely to develop anemia. 2. Infection: Blood collection often has standardized operating procedures and requirements, but for some informal institutions or institutions that do not follow the standard requirements for blood collection, blood donors may be infected with infectious diseases, such as AIDS, Hepatitis B and so on. 3. Other Adverse Reactions: A very small number of people may experience reactions such as dizziness, cold sweat, hematoma, pain or even fainting during blood donation. Normally, blood donation is not harmful to the body and can stimulate the bone marrow cells to produce blood. Donors should fill in the health enquiry form carefully and cooperate with the pre-donation examination before donating blood, and those who do not meet the requirements should give up the current blood donation.