Discussion: Low levels of vitamin B12 have many side-effects, including extreme fatigue.

The liver of cancer patients carries a significant metabolic burden, partly because of drug treatments. Vitamin B12 is stored in the liver. Vitamin B12 deficiency is widespread in cancer patients; it impairs immune system function, nervous system activity, and acute fatigue. The best option to ensure good absorption is B12 injections (Cheap). Vitamin B12 deficiency can be diagnosed through a routine blood test.