- Summary Vitamin B 12 plays a functional role in a variety of organs and body systems and the list of these organs and body systems is growing. According to our working hypothesis (“Master Key Effect”) vitamin B 12 has some unique functions, which are still not accepted; vitamin B12 functions to keep body systems in balance, even under the stress of severe pathology. What is the explanation for elevation of cobalamin level in oncological patients? 1. It is well known that there is a high level of vitamin B12 in different kinds of malignancy. 2. There is a positive correlation between level of vitamin B12 and the severity of the disease, the more severe the disease the higher the level of B12. 3. A number of the experimental laboratory studies indicate an inhibition in the growth of malignant cells upon use of vitamin B12. 4. There are no experimental results indicating the opposite, that vitamin B12 stimulates growth of malignant cells. 5. There is no data about toxic effect of vitamin B12 in the treatment of various diseases. As yet I have not been able to find another explanation for high level of vitamin B12 in oncology patients other than that it is a compensatory mechanism. Perhaps following this body’s “warning sign”, we should start treatment with high doses of vitamin B12 to try to help the stabilization of normal function of the organs and systems. Laboratory researches should be continued to substantiate introduction of cobalamin as preliminary treatment of particular diseases.