Usually, if there is no abnormality after a blood transfusion, it is usually checked three months later, then it can be diagnosed as safe. Because blood transfusion can bring many risks, common risks include allergic reactions, hemolytic reactions, and febrile reactions. These reactions usually occur during or immediately after the transfusion, and after treatment, the patient’s symptoms will be quickly relieved, and after the relief, it can be determined as safe. However, certain diseases transmitted through blood, such as AIDS, Hepatitis B, syphilis, etc., require a longer period of time before it can be found out whether they are safe or not. Especially in the case of AIDS, the window period for HIV infection is about three months, which means that after three months after the blood transfusion, if the blood test is negative for HIV antibodies, it means that the blood transfusion is safe. However, it is not necessarily safe to check within three months.