High serum vitamin B12 levels were found in chronic myeloid leukemia and in acute leukemia with myeloid differentiation. Following x-ray therapy and repeated blood transfusions, a drop of serum vitamin B12 was found.
In chronic lymphatic leukemia, undifferentiated stem cell leukemia, Hodgkin’s disease, and multiple myeloma, the serum vitamin B12 concentrations were normal.
In polycythemia with marked leukocytosis the serum B12 was normal.
In myelosclerosis high B12 values may be found.
The serum vitamin B12 in chronic myeloid leukemia is in a bound form and the binding capacity for added B12 is increased.
Serum vitamin B12 determination may be of some value in differentiating various types of leukemia and other myelo-proliferative disorders.