Anaemia means that the blood has too little haemoglobin to carry oxygen effectively. It is not a single disease. Iron deficiency is common, but anaemia can also result from vitamin deficiency, blood loss, chronic illness, inherited conditions or problems producing or breaking down red blood cells.
Possible symptoms
- Tiredness, weakness or reduced exercise tolerance
- Shortness of breath, dizziness or headaches
- Pale skin or paleness inside the lower eyelids
- Fast heartbeat or palpitations
- Cold hands and feet
- Difficulty concentrating
Mild anaemia may cause no obvious symptoms. A blood test is needed for diagnosis.
Common causes
Iron deficiency may result from heavy menstrual bleeding, pregnancy, bleeding in the digestive tract, low iron intake or poor absorption. Other causes include vitamin B12 or folate deficiency, kidney disease, inflammation, cancer, bone-marrow disorders and inherited conditions such as sickle cell disease or thalassaemia.
Diagnosis
Testing usually begins with a full blood count. Further tests may examine iron stores, vitamin levels, kidney function, inflammation, blood-cell shape and possible blood loss. Finding the cause is essential, particularly in adults with new iron deficiency.
Treatment
Treatment depends on the cause. Options may include oral or intravenous iron, vitamin B12, folate, treatment of bleeding or an underlying disease, and occasionally a blood transfusion. Do not take iron routinely without confirming deficiency because too much iron can be harmful and may delay the correct diagnosis.
When to seek medical advice
Arrange an assessment for persistent fatigue, breathlessness, palpitations, pale skin, heavy periods, blood in the stool, black stools, unexplained weight loss or symptoms during pregnancy. Children with poor growth, unusual tiredness or feeding concerns should also be assessed.
When to seek urgent help
Seek urgent care for chest pain, severe breathlessness, fainting, a very fast heartbeat, active heavy bleeding, vomiting blood or black tar-like stools.
Sources
- World Health Organization: Anaemia
- NHS: Iron deficiency anaemia
- Kingston and Richmond NHS Foundation Trust: Anaemia
Reviewed: 28 August 2026