You cannot lose weight by donating blood. Blood donation is done by making the blood in the veins to be drained out of the body through intravenous injection. However, this method only reduces the blood cells in the blood, such as red blood cells, platelets, white blood cells, etc. It does not take away fat, so it does not cause a reduction in fat and further weight loss. Donating blood may cause weight loss for a short period of time, but it is mainly the water and blood cells that are lost and has nothing to do with fat. To lose weight you still have to rely on exercise and diet, and it is only through persistent efforts under the guidance of scientific theories that weight can be reduced. Human body fat is mainly stored in the abdomen, buttocks, thighs and other parts of the human body, in order to make weight loss successful, should make these places where fat is stored fat reduction, cell thinning in order to lose weight.