How an iron deficiency affect the composition of blood?

Less red blood cells: Iron is involved in the formation of red blood cells essential for carrying oxygen in the blood to the body. Iron deficiency anemia results from low iron & thus blood composed of less red blood cells. This results in symtoms which may include pallor, fatigue, weakness, lightheadedness, anxiety, irritability, depression, heart palpitations, & muscle twitching.

Reduced Red cells: Iron is required in order to make hemoglobin which is carried in the red blood cells(rbc). So iron deficienncy leads to reduced size and number of rbcs and low hemoglobin level or anemia, is the end result.