Anemia | |
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Other names | Anaemia, erythrocytopenia |
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Blood smear showing iron-deficiency anemia, with small, pale red blood cells. | |
Pronunciation | |
Specialty | Hematology |
Symptoms | Feeling tired, pale skin, weakness, shortness of breath, feeling faint[1] |
Causes | Blood loss, decreased red blood cell production, increased red blood cell breakdown[1] |
Diagnostic method | Blood hemoglobin measurement[1] |
Frequency | 2.36 billion / 33% (2015)[2] |
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen. This can be due to a lower than normal number of red blood cells, a reduction in the amount of hemoglobin available for oxygen transport, or abnormalities in hemoglobin that impair its function.[3][4]
The name is derived from Ancient Greek ἀν- (an-) 'not' and αἷμα (haima) 'blood'.[5] When anemia comes on slowly, the symptoms are often vague, such as tiredness, weakness, shortness of breath, headaches, and a reduced ability to exercise.[1] When anemia is acute, symptoms may include confusion, feeling like one is going to pass out, loss of consciousness, and increased thirst.[1] Anemia must be significant before a person becomes noticeably pale.[1] Additional symptoms may occur depending on the underlying cause.[1] Anemia can be temporary or long term and can range from mild to severe.[6]
Anemia can be caused by blood loss, decreased red blood cell production, and increased red blood cell breakdown.[1] Causes of blood loss include bleeding due to inflammation of the stomach or intestines, bleeding from surgery, serious injury, or blood donation.[1] Causes of decreased production include iron deficiency, folate deficiency, vitamin B12 deficiency, thalassemia and a number of bone marrow tumors.[1] Causes of increased breakdown include genetic disorders such as sickle cell anemia, infections such as malaria, and certain autoimmune diseases.[1]
Anemia can also be classified based on the size of the red blood cells and amount of hemoglobin in each cell.[1] If the cells are small, it is called microcytic anemia; if they are large, it is called macrocytic anemia; and if they are normal sized, it is called normocytic anemia.[1] The diagnosis of anemia in men is based on a hemoglobin of less than 130 to 140 g/L (13 to 14 g/dL); in women, it is less than 120 to 130 g/L (12 to 13 g/dL).[1][7] Further testing is then required to determine the cause.[1][8]
Treatment depends on the specific cause. Certain groups of individuals, such as pregnant women, can benefit from the use of iron pills for prevention.[1][9] Dietary supplementation, without determining the specific cause, is not recommended.[1] The use of blood transfusions is typically based on a person's signs and symptoms.[1] In those without symptoms, they are not recommended unless hemoglobin levels are less than 60 to 80 g/L (6 to 8 g/dL).[1][10] These recommendations may also apply to some people with acute bleeding.[1] Erythropoiesis-stimulating agents are only recommended in those with severe anemia.[10]
Anemia is the most common blood disorder, affecting about a fifth to a third of the global population.[1][2][11][12] Iron-deficiency anemia is the most common cause of anemia worldwide, and affects nearly one billion people.[13]
In 2013, anemia due to iron deficiency resulted in about 183,000 deaths – down from 213,000 deaths in 1990.[14] This condition is most prevalent in children[15] with also an above average prevalence in elderly[1] and women of reproductive age (especially during pregnancy).[13] Anemia is one of the six WHO global nutrition targets for 2025 and for diet-related global targets endorsed by World Health Assembly in 2012 and 2013. Efforts to reach global targets contribute to reaching Sustainable Development Goals (SDGs),[16] with anemia as one of the targets in SDG 2 for achieving zero world hunger.[17]