Radiation during a CT examination is mildly harmful to the human body, and once in a while it does not have a significant effect on the human body. However, if the CT examination is conducted frequently and for a long time, it will cause serious damage to the immune function and organ function of the human body. 1. Immune function: If CT radiation accumulates to a certain extent in the body, it will destroy a large number of human white blood cells, so that the number of white blood cells in the human body decreases, which leads to a decline in the body’s immune function. 2. Damage to organ function: CT radiation can also cause damage to human sex organs, eyes and thyroid gland. Long-term CT radiation may also lead to genetic mutations or affect fertility. Therefore, in order to avoid unnecessary harm to the human body, follow the doctor’s instructions for examination. At the same time, it is important to avoid non-essential examinations for contraindicated groups, such as pregnant women or infants.