Anemia (also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood,or a lowered ability of the blood to carry oxygen.When anemia comes on slowly, the symptoms are often vague and may include feeling tired, weakness, shortness of breath, and a poor ability to exercise.When the anemia comes on quickly, symptoms may include confusion, feeling like one is going to pass out, loss of consciousness, and increased thirst.Anemia must be significant before a person becomes noticeably pale. Additional symptoms may occur depending on the underlying cause.
Anemia can be caused by blood loss, decreased red blood cell production, and increased red blood cell breakdown.Causes of blood loss include trauma and gastrointestinal bleeding.Causes of decreased production include iron deficiency, vitamin B12 deficiency, thalassemia, and a number of neoplasms of the bone marrow.Causes of increased breakdown include genetic conditions such as sickle cell anemia, infections such as malaria, and certain autoimmune diseases.
Certain groups of individuals, such as pregnant women, benefit from the use of iron pills for prevention.Dietary supplementation, without determining the specific cause, is not recommended. The use of blood transfusions is typically based on a person's signs and symptoms.In those without symptoms, they are not recommended unless hemoglobin levels are less than 60 to 80 g/L (6 to 8 g/dL).These recommendations may also apply to some people with acute bleeding.Erythropoiesis-stimulating medications are only recommended in those with severe anemia.