Anaemia refers to a lack of red blood cells or haemoglobin (the oxygen-carrying protein) in the blood and has many causes. Anaemia can come to light because of tiredness and shortness of breath, but frequently there are no symptoms and the problem is identified on blood testing. Anaemia may result from failure to absorb iron or vitamins properly from the gut (malabsorption), as may happen in a variety of gut disorders, including coeliac disease and inflammatory bowel disease. Iron deficiency anaemia is often due to slow bleeding from the gut, eg from an ulcer in the stomach or a polyp or cancer in the bowel. Medications such as aspirin which thin the blood, or anti-inflammatory drugs, can cause blood loss from the gut leading to anaemia.
Iron deficiency anaemia is regarded as one of the key "alarm symptoms" for cancer of the digestive system and usually will require urgent investigation. Investigating the cause for anaemia is a major part of gastroenterology practice, and usually involves endoscopic tests such as gastroscopy and colonoscopy, sometimes together with scans and capsule endoscopy (in which the patient swallows a minature pill-camera to examine the small intestine)
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