Sudden dizziness when donating blood may be caused by psychological factors or insufficient blood supply to the brain.
1. Psychological factors: psychological tension or fear when donating blood may cause vagus nerve excitation, which may suddenly cause dizziness, possibly accompanied by nausea, should improve the psychological state, reduce the tension and fear of the psychological, bed rest, and usually can be improved on their own.
2. Insufficient blood supply to the brain: when donating blood, donating a large amount of blood, such as 400ml or 800ml, may cause insufficient blood volume in the body, resulting in low blood pressure, which leads to abnormal blood supply to the brain, inducing insufficient blood supply to the brain, and then dizziness will suddenly occur.
If dizziness occurs suddenly when donating blood and lasts for a long time, you should consult a doctor for appropriate examination to clarify the specific cause and carry out appropriate treatment under the doctor’s guidance.