MCH (mean corpuscular haemoglobin) measures the average amount of haemoglobin contained within a single red blood cell. It is a derived index calculated from the haemoglobin concentration and red blood cell count. MCH provides information about whether red blood cells are adequately filled with haemoglobin.

Low MCH (hypochromic cells — pale red blood cells with less haemoglobin) is most commonly caused by iron deficiency anaemia or thalassaemia trait. High MCH (hyperchromic cells) is associated with vitamin B12 or folate deficiency, where red blood cells are larger than normal (macrocytic). MCH is interpreted alongside MCV and MCHC to characterise the type of anaemia present.