Medical Encyclopedia › A › Anaemia
Anaemia means that the blood contains too little haemoglobin, the red pigment that carries oxygen, or too few red blood cells. As a result, less oxygen reaches the organs. Anaemia is not a disease in itself but a finding whose cause should be identified.
How does anaemia show itself?
Mild anaemia often goes unnoticed. As it becomes more marked, typical complaints are tiredness, reduced exercise tolerance, pale skin and mucous membranes, breathlessness on exertion, palpitations, dizziness or headache. When anaemia develops slowly, the body adapts surprisingly well to low values.
When is it called anaemia?
Haemoglobin is measured as part of a full blood count. The World Health Organization uses these thresholds for adults:
| Group | Anaemia if haemoglobin is below |
|---|---|
| Men | 13 g/dl (130 g/l) |
| Women (not pregnant) | 12 g/dl (120 g/l) |
| Pregnant women | 11 g/dl (110 g/l) |
Reference ranges vary slightly between laboratories, and results are always interpreted by a doctor together with symptoms and previous findings.
Common causes
Worldwide, the most common cause is iron deficiency, for example from heavy periods, hidden bleeding in the gut or low intake. Other causes include a lack of vitamin B12 or folic acid, chronic inflammation, kidney disease, increased breakdown of red cells (haemolysis) and, less often, bone marrow disorders.
Finding the cause
The size of the red cells (MCV) is a useful clue: small cells suggest iron deficiency, large cells point towards vitamin B12 or folate deficiency. Ferritin, reticulocytes, inflammatory markers and kidney values are often checked as well. Treatment depends on the cause; taking iron without a proven deficiency is not advisable.
Frequently asked questions
Is anaemia dangerous?
Mild forms often cause only tiredness. Finding the cause matters most, because blood loss or other diseases may be behind it. Severe anaemia strains the heart and circulation.
How do you recognise anaemia?
Typical signs are tiredness, pallor, poor concentration, headaches and breathlessness on exertion. Only a blood test can confirm it.
What helps with iron deficiency anaemia?
Iron supplements as prescribed by a doctor and treatment of the cause. Iron-rich foods such as meat, pulses and wholegrains help, but are usually not enough for a genuine deficiency.
How quickly do iron tablets work?
Haemoglobin usually rises within a few weeks. To refill the iron stores, treatment is generally continued for about three months.
Related terms
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Go to the Medical QuizSources
- WHO: Guideline on haemoglobin cutoffs to define anaemia in individuals and populations (2024)
- Onkopedia guideline Iron deficiency and iron deficiency anaemia (DGHO, Germany)
- WHO: Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity (2011)
This entry is for general information only and does not replace medical advice. Last updated: November 2026.