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Why can anemia cause pale skin and tiredness?

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blood disease Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.

Anemia occurs when the blood’s capacity to carry oxygen to tissues is reduced, either because red blood cells are deficient in number or because they lack sufficient hemoglobin.12

The symptoms of tiredness and weakness arise because the body’s tissues are not receiving adequate oxygen. In response to this deficit, the heart must increase its rate to circulate blood more rapidly, and the lungs increase the respiratory rate to capture more oxygen, both of which contribute to a sense of fatigue.12

Pallor, or pale skin, occurs because the blood is less saturated with the red pigment hemoglobin. This lack of pigment is most noticeable in the skin, mucous membranes, and nail beds. While these symptoms are common indicators of the condition, the severity of the experience often depends on how rapidly the anemia develops; gradual onset may allow the body to compensate more effectively than a sudden, rapid decline in blood values.123