Anemia is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a decreased ability of the blood to carry oxygen. When anemia occurs slowly, the symptoms are often vague and may include feeling tired, weak, difficult to breathe or poor ability to exercise. Fast-onset anemia often has major symptoms, which can include confusion, a feeling of fainting, loss of consciousness, or increased thirst. Anemia should be significant before a person becomes visibly pale. Additional symptoms may occur depending on the underlying cause.
The three major types of anemia are due to blood loss, decreased red blood cell production, and increased red blood cell breakdown. Causes of blood loss include trauma and gastrointestinal bleeding, among others. Causes of decreased production include iron deficiency, lack of vitamin B12, thalassemia, and a number of bone marrow neoplasms. Causes of increased decomposition include a number of genetic conditions such as sickle cell anemia, infections such as malaria, and certain autoimmune diseases. It can also be classified according to the size of the red blood cells and the amount of hemoglobin in each cell. If the cells are small, it is microcytic anemia. If they are large, it is macrocytic anemia, whereas if they are of normal size, it is normocytic anemia. The diagnosis in men is based on hemoglobin less than 130 to 140 g / l (13 to 14 g / dL), while in women it should be less than 120 to 130 g / L (12 to 13 g / dL). Further tests are then required to determine the cause.
Some groups of individuals, such as pregnant women, benefit from the use of iron pills for prevention. Dietary supplementation is not recommended, without determining the specific cause. 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 drugs are only recommended in people with severe anemia.
Anemia is the most common blood disorder, affecting one-third of the world's population. Iron deficiency anemia affects about 1 billion people. In 2013, iron deficiency anemia produced about 183,000 deaths, compared to 213,000 deaths in 1990. It is more common in women than in men, during pregnancy and in children and the elderly. Anemia increases the costs of medical care and reduces a person's productivity through a decrease in work capacity. The name is derived from the ancient Greek: ἀναιμία anaimia, meaning "lack of blood", from ἀν- an-, "not" and αἷμα haima, blood.