Blood test

Recently a nephew who is 7+ of age had to undergo some blood test. A small syringe was inserted into his nerve and then the sample was collected. One full syringe of blood was extracted out of his body. He was petrified with the realization that one whole syringe of blood is lost from his body; with loads of concern he approaches his grand-mom and asks will they return the balance blood after the tests are over? He was even more shocked to know that it will not be returned and he had a worried face, to console him his grand-mom told him don’t worry the lost blood will be generated in your body in a few days. He promptly goes and checks his weight without others knowledge. After a month one fine day he comes to his grand-mom and says my weight is still the same, the lost blood is gone saying this he start crying