Anemia, which occurs when the number of red blood cells reaches critically low levels, results from multiple myeloma because it causes the suppression or crowding out of healthy red blood cells. The most common side effect of anemia is an overpowering feeling of fatigue that may not break even with healthy diet, ample rest, fluids, or stimulants like caffeine. This feeling of general exhaustion can last for days or even weeks at a time.
However, it should be noted that anemia is not only related to multiple myeloma and the development of bone marrow cancer. It can result from a number of other health conditions, from pregnancy to menstruation and iron and vitamin deficiency. Simply failing to get enough iron in the diet can cause anemia.