What substances are necessary for the formation of hemoglobin and red blood cells, and what can result from their deficiency?

Substances necessary for the formation of hemoglobin and red blood cells include iron, vitamin B12, folic acid, copper, pyridoxine, cobalt, and nickel. A deficiency in any of these substances can lead to anemia, which results in reduced numbers or function of red blood cells and unmet tissue oxygen needs.