Following are the common cause of severe anemia
- Nutritional.
- Hookworm infestation.(in developing countries)
- Hemetemesis and melaena (commonly from chronic duodenal ulcer or rupture of oesophageal varices
- Chronic bleeding haemorrhoids.
- Aplastic anaemia.
- Acute leukaemias.
- Thalassaemia.
- Uraemia.
- Menorrhagia.
- Carcinoma of stomach, lung, colon.
- Blood Transfusion is usually required when haemoglobin level goes below 7 gm/dl.