Macrocytosis means that the red blood cells are larger than normal. Macrocytic anaemia occurs when there is also a fall in haemoglobin levels in the blood. Anaemia is usually defined as a haemoglobin level of at least two standard deviations below the mean for that age and sex. By this definition, 2.5% of a normal population will be classified as anaemic. The figures are usually taken as below 13 g/dL for men and below 12 g/dL for women. Children have a lower haemoglobin than adults.
This is a companion discussion topic for the original article at https://patient.info/doctor/haematology/macrocytosis-and-macrocytic-anaemia