You will not lose weight after donating blood because blood donation is a process whereby one’s own blood is drawn through a vein and contributed to clinical applications. When donating blood, the body loses some of its blood cells and some of its plasma, but this loss is temporary and can usually be restored to the pre-donation level after a week or so. Wasting refers to the decrease in the number of fat cells in the body, which cannot be realized through blood donation. The main way to lose weight is to control the diet through proper exercise, which causes a reduction in the number of fat cells in the body, and that is the only way to lose weight, so blood donation will not cause weight loss. If a patient experiences wasting, do not assume that it is caused by blood donation; there may be other reasons. If there is no specific exercise or deliberate diet control, the wasting should be alert to whether it is a metabolic disease, such as diabetes, hyperthyroidism, etc., and need to go to the endocrinology department for further examination.