Anemia is a condition in which the blood has a reduced amount of hemoglobin and/or red blood cells, so tissues receive less oxygen. It is not a separate disease but a syndrome: there is always a specific cause behind it that is important to find.
The most common form worldwide is iron-deficiency anemia due to iron deficiency. But anemia also occurs with vitamin shortages, destruction of red blood cells, chronic diseases and bone marrow damage.
What happens in anemia
Red blood cells carry oxygen thanks to hemoglobin. When there is little hemoglobin, organs get less oxygen — hence fatigue, shortness of breath, pallor, palpitations and reduced performance. The severity of symptoms depends not only on the hemoglobin level but also on how quickly it fell: with slow development the body has time to adapt.
Main types and causes
By cause, anemias fall into three large groups: from impaired production of red blood cells (deficiency of iron, vitamin B12 and folate, bone marrow disease, chronic kidney disease), from loss of red blood cells (bleeding, including hidden gastrointestinal bleeding and heavy periods) and from destruction of red blood cells (hemolysis).
The size of the red blood cells helps clarify the form of anemia: microcytic (small cells — most often iron deficiency), normocytic (chronic disease, blood loss) and macrocytic (lack of B12 or folate).
When to get tested
Reasons to check your blood: persistent fatigue, pallor, shortness of breath on exertion, brittle nails and hair, cravings for unusual foods or ice. The basic step is a complete blood count; if anemia is found, the doctor adds ferritin, iron studies, vitamin B12 and folate, and, if needed, looks for a source of blood loss. Treatment targets not 'anemia in general' but its cause.
Reference ranges
Hemoglobin thresholds below which the WHO diagnoses anemia (venous blood, sea level):
| Men (adults) | < 130 g/L (13 g/dL) |
| Non-pregnant women | < 120 g/L (12 g/dL) |
| Pregnant women | < 110 g/L (11 g/dL) |
| Children 6–59 months | < 110 g/L |
| Children 5–11 years | < 115 g/L |
Calculate using this marker
Calculators where Anemia is used directly:
Frequently asked questions
Are anemia and low hemoglobin the same thing?
Practically yes: anemia is defined precisely by reduced hemoglobin. But low hemoglobin is only a signal; it is important to find the cause (iron or vitamin deficiency, blood loss, destruction of red blood cells).
Can anemia be cured with diet alone?
Sometimes mild iron deficiency is corrected with diet, but more often iron or vitamin supplements are needed, along with removing the cause (for example, a source of blood loss). Nutrition is a support, not a replacement for treatment.