The state in which the blood hemoglobin level is below the normal range for the patient's age and sex is referred to as anaemia. At birth, the level is 20g% and drops over the next 3 months to about 16g%. The adult male has a 2g% higher hemoglobin level compared to the female due to the stimulus of androgens on erythropoesis. A level below 12g% in a male and 10G% in an adult female must be considered as anaemia.

The cause of anemia may be due to acute or chronic blood loss, inadequate production of red blood cells by the bone marrow or due to excessive destruction of red blood cells. Most anemias are however multifactorial. In India the condition is usually nutritional or due to chronic malaria/kala azar, and worm infestations of the gut. Amongst women, excessive menstrual blood loss and pregnancy are the commonest cause of the condition. Anemia is also seen in kidney disorders, endocrine deficiencies, leukemias and cancer, and chronic inflammation and infection states. Ingestion of drugs like aspirin can cause gastric ulcer bleeds and exposure to radiation can depress the bone marrow. Symptoms and signs of anemia are fatigue, breathlessness, palpitations, anginal pain, dizziness and tingling/numbness at feet and hands. The patients is classically pale looking and may have swelling of feet, dilated heart with flow murmurs and rapid heart rate. Diagnosis of anemia is based on a simple blood test to determine blood hemoglobin levels and also examining a stained blood smear to detect color and shape of red blood cells.