An elderly man has been receiving weekly injections of vitamin B12 ever since nearly all of his stomach was removed 6 months ago because of stomach

An elderly man has been receiving weekly injections of vitamin B12 ever since nearly all of his stomach was removed 6 months ago because of stomach cancer. Why is he receiving the vitamin injections? Why canât the vitamin be delivered in tablet form? What is the function of the vitamin in hematopoiesis?